As long as the party isn't dying I don't care what the healers do. As long as the tank is holding aggro and keeping the mob standing still as much as possible, I don't care what they do. IMO, the "healers and tanks NEED, key word need, to dps" mentality spawns from the raid community and spreads to every other part of the community. Since raiders are trying to clear everything as quick as possible and being unwilling to wait to get better gear to get better dps from their dps, they make the healers and tanks try to dps as much as possible as well. This mentality spreads to the rest of the community in much the same way the "PLDs and MNKs are useless and should be deleted from the game" mentality spread.

Some people don't care about speed running everything in the game. They come home from a long day at work and log in looking to relax and maybe get a few things done before time for bed. This is a video game, not a job or a competitive sport. People don't need to always operate at 110% in every aspect of this game, raiding / pvp excluded, maybe.