On-disc DLC, why?

So, I got into an old argument with a Gamestop employee about downloadable content.  Specifically, it was about the not-so-downloadable kind that you have to buy to unlock from the disc.  At first, this sounds like a really bad idea.  The idea of DLC, at least to the consumer, is that you initially bought a complete game, and the company later creates new stuff to plug into it.  So, why are they now making DLC right on the game disc itself, making you pay to access it, and is it right?
* First, let's be clear about the motive.  Capcom was recently hit with this controversy when it was discovered there were extra characters on the disc of Street Fighter X Tekken that were supposed to be available by DLC.  They responded to the discovery via a blog post, which I discovered by Event Hubs.  According to Capcom, they wanted to ensure compatibility with those who didn't buy the characters without having to patch the game (which as Skyrim has shown us, can create problems of its own).  They also say it reduces the file size of future downloads, because some of it is already there and just needs a much smaller unlock file.  Those were the reasons that apply to all developers, so I'll stick with those for this argument.

Rather than follow the traditional argument formula, I'll go right to the biggest issue brought up right there.  When you patch things in, it really can cause a lot of problems of its own.  Skyrim is a good example of how this can fail, and they haven't even had DLC yet!  In attempting to patch problems with their game, they actually ended up completely negating natural resistances characters have and even made dragons fly backwards.  The dragon thing's weird, but not crucial.  The resistances however, are a major part of the game to lose.  Monday Night Combat also suffered because of DLC.  When they made their only DLC for the Xbox 360, they also put some things in that they felt would help balance the game, only to find out they just broke the game more, and the rookie developer with relatively little cash was unable to ever make any new patches to fix it.  Finally, as anyone who follows any kind of technology seriously (let's say Windows) knows, you can never truly patch away all the problems.  When you introduce new DLC, you have to go through a lot of work to make sure it all complies with the rest of the game, and with how big video games are, it's easy for that to go wrong.  By making your first DLC on the disc, already compatible with everything (otherwise why would you release it yet?), you forestall that obstacle longer so you have more time to get feedback from your customers.
As for file size, this really depends on how you play your games.  If you tend to install your games to the hard drive for faster loading times, then this just might increase the file size slightly.  I can't really be sure, since I don't know how much they have to pack into DLC just for the sake of compatibility.  However, it's impossible to deny that this makes the act of downloading it much faster.  People with slow connections will have a much easier time getting to it.  It also makes this much easier for transport.  If you're the type to take your online profile with you to other consoles, then I know I'd prefer to have a tiny unlock code on my flash drive than the big chunk of actual stuff.  Of course, those who don't install games to your hard drive in the first place will definitely notice the sizeable difference in space.

So that's the technical benefits to on-disc DLC.  Now we come to the business side.  Consumers like to cite the analogy that no other non-data product is partly unusable until you pay more money.  I'd like to first say that computer software (as all video games are) is entirely different in nature from other products, but that's not even the important issue.  The underlying idea here is that if you physically have something (again, software isn't exactly physical except for the microscopic 0's and 1's), you should be able to use it right away once you've bought the physical media.  I'd like to state that pirates already do this and that it's a rather booming practice.  Those complaining are of the more moral variety.  To those people, I give you another scenario.  You already know that this stuff is completed, on the disc, and you can't access it yet.  What if the company completed it, did not put it on the disc, and didn't tell you about it until it was officially released?  You have literally the same amount of access for the same amount of time with the same level of completion in both scenarios.  The only difference is that in the first scenario, you knew about it because someone was crafty enough to hack it out.  Would you rather have no access to it at all?  The Gamestop employee to whom I spoke actually answered "yes" to that question, by the way.
Of course, the followup idea most people offer is that this extra thing should be free.  They believe whatever you put on the disc should be accessible to whoever buys it.  Again, the real problem is your level of knowledge about the game.  The developer is always in control of exactly how much you get when you buy things from them.  Since you're acting as the consumer, the real question is always "is this a good deal for your money?"  Well, is it?  Do you like the game?  Is what you initially got worth the money you paid to get it?  This is all about your personal entertainment, remember.  If the answer is "no," you have every right not to buy it.  That's why there are reviews for these products everywhere.  Let's face it, for most of you the answer is still usually "yes," it's worth the money.  Saying the extra stuff they put on the disc should be free is almost literally saying that any future downloadable content should be free.  It's exactly the same stuff, just a matter of where it's kept, and it all comes to business.  Any perceived "morality" is marketing and public relations.  All businesses will calculate how much money they can realistically extract, and generally try to control how much information the public has about their products.

Based on that, no, the game companies did not finish a product and then figure out what they should cut out to make more money.  As much as I hate corporations (I refuse to do any business with AT&T, Xbox Live, PSN, or Netflix), I have to side with them on this.  They actually finish a product, figure out what extras people would like, and then put it on the disc itself as a matter of convenience.  They are under no obligation to use every last bit of space on the disc, either.  It always comes down to whether the product is worth the purchase.