I don't think its a matter of how often a bug occurs...
Its more of a safety feature...
its like saying, 'why does my car need airbags? when I've never had a crash?', or, 'why do i keep a system restore point? when my pc never crashes?'
the whole idea of the auto-update feature is to ease the updating process... so doesn't it make sense to ease the reverting process, if a bug occurs?
Cause at the moment you have to, locate the build on the forum, download it, then rename it *optional i guess*, close HFS, delete or overwrite hfs.exe, then execute.
Admit it, it is much easier just to hit a revert build button? to keep that ease of use...