they are not exactly a must to me. When I was doing Fema work in texas and speed was a big big issue, I rapidly found myself losing a lot of gear. no pulleys, no rings, no tangling strings.
it all depends on the type of work environment your in. Pulleys and things are good for your body but they can slow you down a lot. Mentally as well.
Fro the most part it was a lot of up and down climbs for one or two broken or hangers.
I found the fastest way to aproach the tree was as follows.
throw line, do not isolate, pull line over, tie off to tree. Footlock single line, decend single line and boom.