In fact, getting rid of vacuum full, or changing it to work like cluster, has been proposed in the past. The use case really is pretty narrow; cluster is a lot faster if there's a lot of unused space in the table, and if there's not, vacuum full isn't going to do much so there's not much point running it in the first place. The reason it exists is largely historical, there hasn't been a pressing reason to remove it either.
I can assure you it is a great way to get back gigabytes when someone has put no vacuum strategy in place and your 200K row table (with about 200 bytes per row) is taking up 1.7gig!!! Vive le truncate table, and vive le vacuum full! :-) Anton
