I don't drive planes nor busses. I'm a passenger: The back seat(s) of passenger cars are often fixed too. I wouldn't be surprised to find that the bus driver's seat is powered.

I do drive cars, though, and sometimes other people's cars. I'd much rather be able to adjust while driving so that I can have better control over the car than have to fumble with levers, which might propel me back far enough that I cannot brake. Heck, I might have been having to adjust because I didn't realize how far i needed to press the brake in the first place.