No, I'm pretty sure lowering the landing gear can change the aerodynamic properties of an aircraft pretty significantly. You wouldn't ever want that to happen unexpectedly.
You'd be right. Next time you're flying, pay attention when the gear goes down. You'll hear an increase in wind noise, coupled with more vibration. The airplane will also kinda "sag" from the increased drag.
It would be interesting to deploy the nose gear only when the main gear is in contact with the ground. You'd get better aerodynamic properties that way, because you'd never fly with the nose gear down.
But in that case if the nose gear fails to deploy you're likely past the point where you can throttle up and try again. If you try to lower the gear while you're still in the air and the gear doesn't go down, you can circle back and try again.
It's not supposed to fail. Anything could fail, and yeah that sucks. If it fails on the first try, it will probably fail on the second try.
Landing with gear up happens sometimes, and pilots are supposed to do a decent job with it. Large passenger jets have done this and been put back into service after repairs.
Failure can be detected. Throttle up, and any other needed adjustments, can be done immediately by the computer. Getting up off the runway again can be automatic.
Not exactly true. Many airplanes have manual gear release systems if the mechanical systems fail [1]. These systems don't always work, true, and they may still have to land gear-up true, but there is a manual fail-over system and it does have to be used occasionally. If the rear wheels are already down, though, it's too late to try this.
Aviation is not the type of industry where "failures can be handled automatically by the computer" is an acceptable answer. There's almost always manual systems in place for when the computers fail, which they do.
