Most people that rely on potions don't pop fly potions consistently, only when they know there is a fight. This means lots of targets are able to be tripped initially.
You can't jump someone with a throw.
The assassin or thief has the ability to surprise the victim.
Open with trip, and if they're flying, nothing really lost since it won't work and combat won't initiate (I think). If it lands, go to town.
Maybe Jalim likes it because it is an opening move that lags the person, and if that person has stacked a few movement commands, even better.
It also allows you to chase and reengage with a lag move for sealing people that do get off a flee.

Throw may be better situationally, but trip is also quite deadly to certain people. Just not maran, arials, clouds, transmuters, druids, conjurers (unless archons lost the fly supp along with healers) and outlanders presumably have windwalk up and anyone that can out tank you.