Let's say you buy a game for $60 and enjoy it a ton. You start going to tournaments and become totally involved. When Capcom releases 12 new characters who are likely going to be tourney legal, you can't really choose not to buy them unless you are willing to just stop playing. There's a bit of a wrinkle there that I don't have the time or energy to get into, but I'd just like to point out that Capcom is also benefiting from that sort of pressure on semi-professional players that need to stay current.
This is minor at best, because people who get seriously involved in anything are going to be willing to spend money to keep updated. This is true in card games, sports (newest gear / clothes / shoes), etc.; why not video games?
And if your point is that on-disc DLC promotes bad market practices... then I can see that. But what would you plan on doing about it? On-disc DLC can be beneficial, and boycotting all on-disc DLC probably won't solve the problem.
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The Many Forms of Kobe:
http://i39.tinypic.com/oqx98z.jpg -- credit to KIRBEH