Why are low standards for dps acceptable?

[Reilyn]

In LFG in WoW? Hardly

Actually yes. Most of the playerbase had it downloaded.

Recount has been among the top 3 most downloaded addons from curse client for over 8 years.
I had it.
All of my friends had it.
Entire guilds had it.
Any random player that knew of the curse website had it.
If your dps sucked, everyone will know, which also bred competition, and drive to do more damage than your piers. A drive that's nearly non-existent partially because of the fear of being banned for violation of ToS

Yes, meters may be used as a tool to antagonize players, or create habits like tunnel visioning, and greed, but at least the fact that your damage compared to everyone else's is right there for all to see. You'd want to not suck at your class, or else you'd be the butt of jokes. But guess what? People were motivated to do better because of it!