There are lots of crates that collapse when you don't need them -- both soft-sided and wire.
We crate the 2 smaller dogs, simply because they won't ride quietly and we don't want them running around. Jed, our 65# Lab, lays on the floor behind the 2 crates in the hallway by our bathroom. He has NO interest in being anywhere near the front of the rig. However, we carry a collapsible soft-sided crate if it should become necessary to crate him.
When we stop for the night we set the small crates outside, and the little dogs sleep wherever they want -- usually on our bed.
But when we sit outside we like to crate them because they enjoy being out, and it keeps them calm. They get lots and lots of exercise when we're camping, so giving them a safe place -- which they like -- to rest is a win-win for us all.
We know of some friends who never crated their dogs when traveling (they have a Class A). Their motorhome died on the freeway once, and when they pulled over, one of the dogs, who had never willingly left the rig, got out and was hit & killed on the freeway. That convinced us that crating the little ones wasn't even a discussion we needed to have.