It's been basically proven that WoW players will do just about anything for purple loot.

The reason the Arena popularity has dropped? It's no longer the easiest source of loot. What does that say about how many people played Arena before because they enjoyed it?

Wintergrasp? Haven't been there in ages, but it offers some pretty decent rewards so I'll tell you there's a much better likeliness that players are going there because of the rewards than because they actually enjoy the experience.

Look at the huge problem Bliz had (and I think still has) with people basically AFK in battlegrounds. Why would people join a battleground if they didn't want to play it? Answer again, rewards. Purple pixels.

It's got pretty much nothing to do with PvP.