Becasue it is highly restrictive.

It's easy to blame AA for conrol over open time limits, but consider:

-PU dumps into open time hogging up headroom

-APA insistance on seniority for that 1% who whined like spoilt children about some mythical perfect trip being pick up by -gads!- someone junior while the sr is in flight.

The trifecta of AA's open time limits, PU drops into open time, and the APA insistance on the washing of trips means a bogged down, cumbersome and totally crap trading environment.

LS's algorithms cut through a lot of that b/s making trades happen in very tight and challenging trading conditions.