I was interested in watching girls piss well before I knew anything about sex, thanks to a couple of nicely naughty girls in the neighborhood where I grew up. The first time I took my pants down with a girl was very exciting because of curiosity and being naughty (we were too young for any sexual reactions) but it was also a little disappointing. After all, I had something to show ... balls, a dick with distinct body and head, and a little pee hole right at the tip. I knew girls didn't have penises (although I don't remember how I knew that) but I didn't know what they had. So there I stood with my equipment exposed, and there she was, similarly exposed, showing only a little slit poking up from between her legs. All there was to see was skin. It just didn't seem fair.
I was very pleased when, on a subsequent occasion, she suggested that we "go pee-pee together" because I figured I'd get to see where her pee-hole was ... she had to have one of those. Alas, disappointment again. Her stream just came out of her slit, although with a lot more force than I had imagined girls would go with. Still, all good things come to those who wait. As our "games" grew in the number of participants, behaviors got a bit bolder. One of the two girls involved agreed to satisfy the boys' curiosity by holding herself open so we could see where her pee emerged. After she did that, the second girl had to rival her feat. So at a young age, I was granted a very intimate knowledge of female plumbing. The thing I remember most was holding a wide-mouth jar we had found somewhere while one of the girls peed into it. I felt it increase in weight and warmth as she filled it up.
Early teen years (after I learned about sex) were a "dry" spell. I was too embarassed to ask a girl if she would let me watch her piss. I was also fully absorbed in getting to second and third base. It was a time for touching rather than watching. In college, however, I dated a girl who was very free-spirited, and when I left the bathroom door ajar one day when I went in to pee after we had sex, she came in behind me and said she wanted to watch me pee. When I was done she invited me to stay and watch her. When I squatted down in front of her, she knew I was interested and gave me quite a show, clearly enjoying it herself. She turned out to be a little kinky and very exhibitionistic. Since then, I've always been alert to what my sex partner's attitude about pee play might be.
I like watching women pee because I'm very voyeuristic, and if a woman is letting you watch her pee, she's showing everything she has. I like exploring a woman's genitals up close and I love to see that sweet little, and sometimes elusive, pee-hole. Also, peeing with a partner has that thrill of being very naughty, and it's also very intimate.
I've enjoyed pee play almost all my life (I'm over sixty now); have not grown tired of it. And it's easier today ... either because with the internet we are learning that there are no taboos and more woman are accepting and willing to experiment, or maybe because I'm associating with older woman who have accumulated broader experiences, or maybe a bit of both. When I was in my 20s, I figured one woman out of three would go along for some pee play. Today it's more like two out of three. It's not a substitute for more "conventional" sex, but it's my favorite form of foreplay. But, if a partner has any other ideas, then I'm up for them, too, because the thing I like most is a partner who is turned on.