because people don't who are only interested in questing don't want to have random ass players from another alliance running in and killing them all the time. I for one don't, if I want PVP, or PVE with the risk of getting ganked, I'll go to cyrodiil. but in the PVE zones I want to be left to my own devices and not fear that a load of VR10's from another alliance are going to camp the area that my next quest is based killing all the low level people trying to finish it. it would just be stupid and frustrating, not fun at all.
and like people have said, the time for those games are over. the people that actually want them are in the minority, and apparently very very loud. if you want a game like this go off and make, don't try and drag this game down with you because you want to feel powerful and validated by ganking people who just want to do PVE.