I am a bi man, and have used glory holes many times, mostly in seedy adult bookstores. The appeal of them to me are, I don't really think most men are all that good looking, but I really admire a nice cock, so it's a win win. Also, sometimes I just want a good blowjob, I would prefer a woman, but if that's not possible, and there's someone out there who wants to suck a cock, why not help them out.