I trim leaves for two reasons ... first to reduce the area the plant has to transpire water, and second to reduce the area they take up in the tray or cloner. Without roots, they get limp in our 30-35 RH really fast, even with a humidifier in the tent, and overlapping leaves from adjacent plants can promote rot. The stubby fan leaves provide enough nutes to build some roots and support the growth tip, without being in the way or their neighbors.
This is the first time I've used Rapid Rooters, we'll see how that goes.