Designing any kind of space vehicle is always a trade off.

The vehicle needs to be light enough to be launched from earth to mars, but durable enough to fulfill its mission goals.

I’m sure if nasa had access to a vehicle that could send an M1 Abram’s sized, solid steel rover to mars, they totally would, but that would probably cost more than a moon mission, and the whole point of rovers is that they’re fairly cheap for the amount of research you can get out of them.

It's lasted this long. I think they made the right decisions. No matter what it is, it's going to be damaged. The goal is to make it still operate despite the damage for as long as possible. The goal isn't to make it last forever, or to never be damaged. The more massive the wheels are the less mass everything else can be, so it's a big trade-off.

Yes rocks are more sharp on planets or moons with no or very little atmosphere because erosion by wind/rain forces is reduced.