I think i wasn't clear enough.
When i wrote delete "everywhere", i was mainly thinking about "internal" files... because one can delete files in an external dir with no problem, but that's not the case for internal files.
In 1.9, you hadn't this problem : old backup files where deleted!
But i've seen several discussion with other people facing the same problem as me : old backup files taking a lot of place, and no easy solution to delete them... hence my other message, with bug reports.