What they all said.
I'm sure if they could sell MLL access to T+ or L Pass holders (for the same price as with a T+ or L ticket), they would.
If they could sell OMW insurance to T+ or L Pass holders, they would.
If they could remember your seat request when you upgrade an L Pass, they would (actually it remembers the request in the sense that the chosen seat is blocked but not in your name for about 20min, then it opens up again).
If they could offer a proper set of connections online (instead of involving an agent) to T+ or L Pass holders, they would.
Well, maybe not the last one because it doesn't actually produce more revenue.
It's all about terrible IT.
=aw
If they could let you change seat assignments online when using a pass.