A long time ago before quickplay was invented, faster respawn servers were the most popular. All our servers had faster respawn times.
However, people kept complaining about it on the Steam forums, so one day, Valve invented quickplay and blocked servers with faster respawn times from receiving traffic from it.
Since then many people have complained to me instead of Valve about slow respawn times. Having any server on fast respawn is a good way to kill off the population because a server can't compete with quickplay. People only join the fullest servers, and almost no one will willingly join an empty server unless they are forced to by quickplay.