Great thread! I do think its different for everyone.
I agree with those who've connected it with tease and denial - for me, tickling is very much linked to eroticism/sex and teasing/tantalizing. (Great to see some like-minded women on here!). Tickling a man's most sensitive member, while both giving him pleasure but denying him the ultimate release, is a huge turn-on for me.
I love hearing a man moan and beg and be vocal about his desires in bed - cock tickling can really get a guy to enter the heights of desperation if the guy is into it. I'm pretty dominant, but don't enjoy pain/degradation. Genital tickling is such an erotic torture that involves using pleasure as a form of torment and I love that idea. I also happen to be one of (the few???) women who are very aroused visually (although I do very much enjoy erotic stories and audio). It wouldn't just be a cock getting tickled that would get me hot, but seeing the guy's entire reaction - or seeing dialogue with the image.
Also, seeing a man's cock go from flaccid to hard - and knowing it's b/c of what I'm doing to him - is also a big turn-on for me. (Especially if he is uncut - it's erotic the way the head peaks out.)
In FICTION (not real life), I also find it incredibly hot if the cock tickling/teasing is accompanied by interrogation or some sort of experiment. Something very erotic about a horny, panicked man fighting his arousal.
I also do enjoy seeing this same type of thing with women. Watching a woman's pussy/clit get tickled/teased in this way is incredibly erotic to me - again, I think for me it's the reactions.
Just my two cents 😉
-Marie