I agree, men / boys who are physically able (clothed or unclothed) and who do not masturbate, either don't have mates are liars or need medical help.
It is not normal, it gives as much bonding pleasure as the primitive instinct we all have of sitting around a fire experiencing the warmth and looking at the flicker of the flames.
And it costs nothing .................
The only experience I have had was at a Boy Scout camp out. After the sex talk was over with, the kid next to me reached over, then it became a mutual mastrabution session, but he pulled back before we could finish. I wanted to continue, but he said no. It felt so good to hold another dick in my hand, feel the difference in size and shape, and bring him pleasure. By the same token, having someone else, 'do me' was so exciting, besides feeling wonderful. I was sorry when he backed out, but now that I am Heteroflexible, I can continue the practice and feel good about it too.