We generally crate-train every dog that stays with us because it usually makes for a happier dog (and human) in the long run. It's a safe way of confining them, and the dogs end up preferring to sleep in the crate, even when they don't have to because it has a den-like feel, which is comforting to them.
But we never made Popeye use a crate. When he still had his hind legs, I was afraid that because they stuck out so much, they would bang against the sides of the crate anytime he tried to shuffle. Also, in order to get into a crate, Popeye would have to lift himself about 2 inches over the bottom edge that protrudes up. I wasn't sure if that was "too much" for him, so we found other alternatives to crates to keep him safely confined when necessary.
There was the baby crib.
Which eventually was traded for a pet stroller.
A baby gate.
And a miniature exercise pen.
So Popeye may have seen every other dog use a crate on a daily basis, but he himself has never been made to.
Well, just a couple of hours ago, guess where I found him.
This is the crate beside my desk where I work all day (and night). Popeye has slept in front of it off and on many times but today was the very first time he actually went in. I didn't force him to or even encourage him, he just hoisted himself in. And the dog bed is actually higher than the bottom screen so he actually had to climb more than 2" to get on top.
Popeye, on his own, has discovered the comfort and security of the crate.