Another disadvantage is that it blows loose items around the ramp.

The idea of powered gear has been tossed around, but there are two points against it: it's heavier, and it's one more thing to go wrong.

Anything that adds weight to the jet is going to increase fuel burn. Not only do you have the motors themselves, but you've also got heavy wiring and control circuits for the massive amount of power it will take to drive the jet.

The complexity argument is simple. You're adding more potential failure modes to the gear -- wheels that won't turn, turn too fast, or turn at different speeds. The drive system has be compatible with the high heat from braking and wide environmental conditions encountered.

So far, tugs are the cheapest option.

BTW, driven gear also comes up with respect to the big puff of smoke when the wheels touch down. It's cheaper to change tires slightly more often than to spin up the wheels.