The flight attendant trade board is an awesome perk.
US Air(ways) pilots have never been able to trade trips, at least since I came along with the Piedmont merger in 1989.
I am told that the restriction is mostly a result of a USAir married couple of pilots who held the same seat, but at vastly different seniority levels. The very senior husband pilot would get a premium block and trade the entire thing to his wife. Then, again using the power of his seniority, he would ride the bid sheet and snap up all the good trips that remained in open flying. (This, of course, coud work for any two pilots with a large seniority disparity. I am told it was a married couple in this instance.) The union agreed that this abuse of the system was unfair, so in typical fashion, the company took the trade privilege away from all of the thousands of pilots in the seniority list. This happened in the 1980s, and the restriction still survives, despite the fact that there are myriad ways to allow trading without allowing the abuse.