I'd rather have the option of buying DLC than not having it at all.
Plus, with DLC it lets you break a few rules in the game. You can't get any characters from XIII in your team without DLC because it would break the story.
Also, if DLC didn't exist at all, what do you think the chances of Ultros showing up in XIII-2 would be?
Same chance as Gilgamesh showing up in FF8.
Showing up in FFVIII was unexpected but since then they've suggested to him wandering the rift and being able to appear in any FF so if we saw him again, it'd be no surprise. Ultros however has no justification for being able to appear in another FF yet