It's not an in-depth answer. It does not say, for example, why bcrypt is more secure than nested SHA1. (I believe it has to do with the possibility to efficiently implement SHA algorithms in GPUs.)
People are using unsalted SHA1, because someone told them in the past "just use sha1". Now someone else tells them "just use BCrypt". Without understanding why, it's nearly impossible to to decide which security policy is sensible. There are many different types of advice competing for attention, and not all of them are good.
Somebody once said fire was composed of phlogistons. Later, different people said that fire was instead a process of decomposing fuel molecules and a release of visible light due to the energy of the chemical chain reactions taking place inside the flame.
The guy who said "phlogistons" was wrong. So was "just use SHA1" guy.
