Finding ones optimum billing rate is nontrivial. It's true that testing the market is far easier for freelances than for employees. But having less overhead still helps. You can quote lower when you're idle, and higher when you're busy. Indeed, you can even take more risk quoting high, because you can better afford to forgo work.

because demping allows you to find clients faster and without additional conversations - some people feel very scared about money-related conversations. I think this behavior is stupid and destructive for whole market.