Yes, in certain cultures in history, it was common for straight men to sleep together and have close friendships (because of that, some biographer somewhere is always trying to figure out Abe Lincoln's sexuality), but I'm not sure about actual cuddling. When I picture cuddling, it is more than just laying down next to each other - it would also involve some gentle stroking and caressing. I think that if a straight man caressed another straight man while reclining together, it would not commonly have been welcome in many historical periods, even if culturally homosexuality was fairly acknowledged or accepted.
However, in my experiences with group cuddling (NOT the organized commercial kind, blech!), yes straight men joined in the puppy pile with both genders - but we were all a bunch of bodyworkers and New Age-y types used to being in various stages of undress together during bodywork retreats and such. We discussed how to keep touch non-sexual and how touch-starved Western culture is. This was back in the 1980s, so these questions and ponderings are far from new.
In one of my training courses (bodywork), we were shown a documentary about touch, filmedin the late 70s or early 80s I think, and one part stayed with me. I hope I remember most of it...
Some scientists (probably sociologists) set up a study at NYC's public libraries. In it, they had placed two people at the book checkout by the exits. When the library members came along to check out a book, one planted checkout person would touch them (just a light tap on the hand or something rather innocuous and hardly noticeable) while the other made a point not to touch them at all.
They had a concealed camera recording these interactions, so they knew who had been touched and who hadn't been touched. Outside, an interviewer would stop those people (the library members) as they exited and ask them their impression of the library. The results were interestingly consistent - every person who had been touched felt the library was a positive experience. Every person who had not been touched was either neutral or negative about it.
Now, I may be mis-remembering some of it. Perhaps it was most and not all the people who were touched, and so on, but you get the point. Hmm, I am going to have to write to some old friends and find out the name of the film.