I see a lot people remove BT Rep, what is the reason?
Not to show off
Many people, specifically non-invite-traders and anyone who doesn't use bittorrent, don't see it as applicable or appropriate to display.
Or maybe it's about hiding their sweet trading history
Only "they" could answer on that
Other than that, there are people who don't make giveaway thread anymore...n thus they have removed their rep. Also, as other stated, some just don't prefer to show off.