At one company it ended up being a temporary closet room with printer supply and all kind of stuff people randomly tossed in to clear the way. At my current company there's so few people using it it smells dusty and closeted to the point it's unusable to relax.
ad-hoc places worked better for me, like small meeting rooms that are unused at noon, actual storage rooms that are actually very clean and tidy compared to temporary ones, or even a park bench when weather is nice enough
My SO doesn't approve of this schedule though, so I do this only on days we're not going to see each other.
There's a few things in American culture, in particular, working against it though: our backwards cultural attitude that sleeping is considered "lazy" (USA is one of the most sleep-deprived population) and the fact that working on little sleep is falsely considered a "badge of honor," even though the occurrence of mistakes made by workers is MUCH higher when said workers are sleep deprived.
At this particular workplace, it took 90 seconds or so for me to walk from my desk to my car, so it wasn't a big deal. I was also used to the routine, and preferred the certainty that no one would ever walk in on me.
But I must say that this only only happens when (a) I am doing something boring and (b) I didn't get much sleep at home. So while cat napping at work is probably better than fighting it, it is more a mitigation strategy than a preferred option.