In terms of the gay scene, there are plenty of factors that have nothing to do with someone being actually ugly {however you define that) or not "super hot" (factors such as age [really big issue... just look at personal ads on cruising websites or that freak show called Craigslist...], facial hair or not, hair color, balding vs. full head, race [Yes, race!], height, body shape, etc.) that determine whether someone will let another guy suck his dick.
I have been turned down plenty of times because of such purely superficial factors or preferences, just for the purposes of a blowjob, mind you, not for a relationship, a love connection or anything else "involved".... of course, I'm not wearing a neon sign around my neck that flashes "Deepthroat for XXL cocks with videos and really good references to prove it"
And despite my initial disappointment in situations like this, I always feel truly sorry for those guys who pick the "hottie" twink or whatever strikes their particular fancy, and then have to settle for bad to mediocre head... if they only knew what they're missing