well, as hata_ph said, home/backupsys stores backups made by the installer and/or vasm. You can delete it if you dont use backups.
As you said, the others are used by some programs, I guess you can move them and do a symlink if you like, but honestly I dont see the point. They always are there on all the distros I used.
Indeed, /home is for users files. I guess dirs like ftp or www or postgres are used by a "public" or "anonymous" user, so they cant be in any specific user dir because of the permissions problem. Obviously, they cant be on any important location, since they are made to be accessed via network, so /home looks like a reasonable place for files accessed or shared by all the users of the system, or by network users, but not owned by any specific user.