hmm, I think that they cant apply the force (make them levitate) to living creatures. In ESB Luke and yoda only controlled a rock, R2, and the X-wing.
Luke force jumped very high during the vader battle, so it probably takes some initial thrust (jump) with his legs. There is also the force push that Dooku did to Anakin which proves that a force push affects humans.
wow, thats hard to come up with an explaination.
Maybe Yoda was just too tired from the battle.
Anakin lifted Padme by her throat.
as well as Vader lifted Needa by his throat some 20 years later. Needa was not exactly flying, and Padme had still her toes to the ground, but over 80%? weight lifting is impressive none the less...
Applied trick, but still performed with The Force,
If throat is ok, why not "grab" from the had? forehead? ass? crotch? Its all about imagination...
Then again, Does the star wars universe even have falling damage?
Obi Wan & Qui Gon jumping at episode 1
Anakin and the highway falling episode 2.
Padme jumping from the "monolith" episode 2.
Windus arena falling episode 3
And so on...
Who can blame them? Thats why there are no railings in their balconies.
hmm, in EP II, When dooku tries to force drop the above rocks on Yoda during the duel, Yoda catches them. So this proves that things that fall can be caught. However, it is non living.
It may be a concentration thing because Yoda tried very hard to stop the big stone pillar from landing on Obiwan and Anakin.
It wouldn't too be hard to believe that Windu could not stop himself from falling out the window cause he just got blasted with lighting after losing an arm. Or perhaps it was the lighting that killed him.
Yoda was pretty tuckered out as he fell and landed, then rolled, and his eyes were closed like he was knocked out. This could be from hitting the ground too as queeq mentioned.