Because it's just as easy to scroll over a WTB thread as it is for any member to pretend that forum doesn't exist and post it in BST.
And it is silly. If you want to buy, sell, and trade - go to a market that does all of these things. I don't need a place to go buy, a place to go sell, and a place to go trade on an internet forum that can easily compile them into one place.
"For me, my family, my friends and skiing, that is for me. That's my life. The joy I get from skiing... that's worth dying for." - CR Johnson