I have one dog crated and one who roams the living room when we are out.
The crated dog is very fond of his crate, he spends time there voluntarily when we are at home, with the door open, and sleeps. It's a good respite for him to get away from the other dog, as obviously when she wants to play and he doesn't it can get annoying for him.
I did orginally have both dogs crated and the bitch was fine for about a year but then started escaping by both nudging the bolts with her nose and bending the doors! I decided to leave her out as I would rather this than her injure herself escaping. The other one has never tried to do this and I am sure he feels more secure in the crate if we are out.
It depends on the breed of dog too. My dogs are staffies, and it would not be a good idea to leave them together uncrated, as a fight (without us there to intervene) could easily escalate and end in serious injury or death for either dog. It is a risk I am not willing to take. Unfortunately I do not have the space to leave them in separate rooms, but they do not like being in separate rooms anyway, so would be worse off if uncrated.
Also, my dog that is crated was a chewer/"destroyer"
when he was younger. I lost skirting boards! Although this didn't bother me too much, but I would not like him to chew through electrical cables and injure himself.
I would like to think that most people who crate their dogs do it for the welfare and safety of the dog.
In the case of your friends' dogs, as long as cables and things are hidden and the room is "dog-proofed", I would have no qualms about leaving either breed with the run of the house, unless it had shown particularly destructive tendencies or insecurity at being left with the run of the house (some dogs get this - my dog hated being left out to the point where he would mess himself). It doesn't necessarily sound like these dogs need to be crated all day but many dogs will sleep all day anyway (mine do) so it probably wouldn't make much difference whether it was in the crate or on the sofa.
Essay, sorry!