Valour items are there for people who are slower at progression or catching up on gear for alts. Whatever way you shake it, spending 1250 valour upgrading from a 434 green or 450/463 blue ring to a dominance offensive 496 ring is a much bigger upgrade than upgrading 8 ilvls on epics you don't have yet, especially since it gives you a massive boost of ilvl to get into lfr faster.
Even upgrading a 463 to a 5.0 daily 489 is a lot better given you don't have high priority upgrades to do like weapons and the high-stat tier pieces, especially since it can be better than things you get lfr and thus last you a while if you're a normal or lfr mode player (I know that as far as normal mode gearing goes, several VP items are BiS at that raiding level). As patches go on you will be getting increasing ilvl valour gear for the same price as before, making it a lot easier to catch up to the lfr curve. They are your consolation/catch up prize for having bad luck in lfr/normals, a level where the majority of players lie.
Everyone was clamouring for the 'required' rep vp items in 5.0 because they were upgrades. The rep vp items will always be upgrades to at least one of the 10 million who play WoW, even though they are useless for a heroic full-bis-before-next-patch raider who has higher ilvl gear already.
I just so happen to be one of those that gets only gold from LFR, be it normal loot roll or charm. I'm also the one that nothing drops for in regular raids, and only gets "off set" pieces because people in my raid feel sorry that nothing actually drops for my class/spec. If it wasn't for valor gear, I would literally have no gear beyond 463 blues. It pains me to have to weigh spending valor on a piece of gear I need to be able to raid, or upgrading another piece of valor gear I bought 3 weeks ago, pushing off for another 2 to 3 weeks of getting nothing but gold until I can replace another blue.
Valor gear has a place because RNG is not a reliable method of gearing for everyone. And since Blizzard can see the numbers on their side of the game, they must also see this to be true or they would not still be including gear at the valor venders, even if the gear is poorly itemized and pretty much garbage for the specs they seem to be aimed at.
Yes, I agree that in a perfect world, there would be no need for crappy gear to blow valor on with an upgrade system in places. However, WoW is still a virtual world where you can't spend points on upgrades if you never receive an item to upgrade in the first place.