See the guy in your avatar. Sits down on the forehand boom gets up and rips it.
The answer is it depends.
Generally though, a player tries to use his legs trunk upper body arm and wrist in all tennis shots.
If you are using your legs well, you will come off the ground on some shots whether you want to or not.
Personally I like to use the legs and I come off the ground sometimes especially on inside out forehands.