What might look like an unnesseccary use of space to you, might mean the world to others yikes11... like jeol said, there are a whole lot of threads that someone is either proud of he/she made, enjoyed participating in, has put a lot of effort in, wants to keep for future reference in things and deleting these could make them sad or even mad as (i.e.) a lot of work gets destroyed. =)
You might think they take up a lot of space, but that's actually not that much, considering AG has enough server space to stash them all and it keeps the forums interesting.
Think of a forum where all locked topics would get deleted... you would enter the forums and see only a few threads per separate forum. Wouldn't that become boring and make you disgard them alltogether? That would be a bad thing, because then the forums would loose their main purpose: having a place where people meet and talk about a wide variety of topics!
