That's because only very few seriously defend a DPS that only spams 1 or 1-2-3 or lets Garuda do his damage while he's on follow. They're lazy and bad, everybody knows and agrees, it's not controversial that they're lazy and/or bad and it's also typically not very controversial whether it's okay to kick them or not. The controversy in those debates stems from using a parser to determine that, rather than observing the DPS in question for it.
When a healer stands still for extended periods of time instead of DPSing however, it's controversial whether they're lazy and/or bad. There are people who think that as long as "they're doing their job", it's okay to not do more. And that's why threads about healers constantly pop up and explode. A thread about lazy DPS would just quickly turn into a general parser debate.
