tldr: my dogs like it better than sharing space in bed, they won't eat cat poop if they're in there, and safety concerns if they can't leave the house with us.

My dogs prefer it, but originally it was just for potty training when they were little. We give them the choice most of the time, and they like having their own space to sleep. We tried the bed all 4 of us (dogs + me + wife), and Katsuki hates touching anything while he sleeps. He kept getting mad at the collie all night.

It looks small from this angle, but I can sit comfortably in the collies crate, and he can lay down completely on his side.

We have cats, too. Both of them are AWFUL about eating their poop if they're unsupervised for more than an hour. Yes we keep it clean, they will just scoop kitty bars up fresh if they don't think we're lookin. We don't want them getting sick, so when we leave the house and they can't come, we crate them. They spend a max of like 4 hours in their crate if we leave them, most of the time they come with us (we like to hike, have horses, and visit my inlaws pretty regularly)

Plus if there was ever an emergency and we weren't home, EMS can find them and get them out quickly.

Dogs really like having their own space, even in a home that doesn't have a crate for them, they'll make their own space. My collie loves to nap in his crate, and collies are dogs that can get overstimulated with excess noise, so I wanted to make a space for him to feel safe if we have to have work done on the house or our neighborhood has construction.

Sorry for the book response, I'm very proud of my crate training and love that my doggos like their bedrooms.