I've had quite a few GFs who enjoyed it, and one "almost stranger".
It never occurred to me until a friend told me had dated a girl a few times in college who told him, "You know what really turns me on, I like watching a guy jack off". So it did it for her. It didn't make sense to me, and didn't seem all that hot at the time. But I thought about it over time.
I guess a couple of years later, I was having sex with a girl I was dating, and I decided to try it. I moved up on my knees and straddled her face and started stroking it. She loved it. She just stared at it. I stopped for a second and took my hand away for some sucking, and she grabbed my hand and put it back on my cock. She started fingering my ass and sucking my balls until I stuck it in her mouth and came. She really enjoyed it all.
After that, I usually touched myself during sex and gauged the reaction. Almost always, if I started stroking my cock, it wouldn't be long until it was being sucked. With one woman, we would fuck and then lay around and talk. After a while, if I started stroking my dick, she would watch, then play with my balls, then suck it. Once she was on her knees sucking my cock, and she stopped and excited said, "Mmm, jack off in my mouth!", so I did.
I had one girl I was seeing, and she bought some new lube. We were in the bathroom when I saw it. I grabbed it and was looking at it. I said, "Let's try it out" and pulled my cock and, lubed up and started stroking. She stood next to me and played with my balls while I jacked off all over the bathroom counter.
I met a woman online, who as dominant. When we met in a bar for the first time, after about 10 minutes, she said, "Let's finish our drinks and go for a drive." As soon as we got in the car, she said, "I would like you to pull around the corner and park, and jack off for me". It was about 4 in the afternoon, and she sat in my passenger seat and watched me stroke it for about 15 minutes. When I was getting close to coming, she leaned over and took the head in her mouth. I shot a big load in her mouth, then she kissed me and passed my cum to me to swallow.