eh.... I think bands with such big back catalogs should not play things like Warped. why would I want to see a band that has so many albums only play for 25 minutes? if I happened to be at Warped (not gonna happen though) I would try to catch the set, but I wouldn't go just for that. tours like this are best for smaller bands with less albums so you can actually get a good taste of all their material. otherwise the band will be leaving out a lot of great material and I am not a fan of that. those kind of bands should be headlining shows.
I agree with you--but only to a certain extent. If you keep headlining shows you aren't going to grow as a band if you're Relient K. At this point in their careers, despite having a deep catalog, I'm sure their fanbase isn't growing all that much. And the same can be said for most of the main stage bands, I'm sure. But playing Warped Tour? Your band plays in front of younger kids that may not have seen your band otherwise.
Also? The set times are now 45 minutes or so for main stage bands, not 25. So it's like a main support slot on a regular tour. Plenty of time to play the "hits," as well as some newer songs. I'd rather see some bands headline a show. But I can also pay $45, see the bands I love play full sets, and the bands I'm "eh" about (Relient K being one of them) play for a few minutes, then go elsewhere.
Warped is best taken if viewed as a "sampler" of bands.