They literally never know how to respond to this question. You might try something more like - Do the coworkers ever get together on their own time? Or How much turn out do you get at company parties? Is attendance required?

My best job I ever had - at least in terms of coworkers - ended up with us going on a camping trip together. We were all genuinely friends. We went out to lunch together. We talked after hours. I have never found that in another group, but those are the kids of questions I'd be asking.

It also helps because toxic places tend to turn people against each other. If the coworkers are basically friends, it's likely not too toxic of an environment.