Whether it be from the bladder, or some random gland, I've always seen squirting as an indicator of loss of control, a complementary fealty to whatever sexual performance is being received. And yeah it's nice to get an objective and outward display from a woman when so many of their sexual mannerisms come with subjective pretense. I don't think it's inaccurate or wrong that a lot of men are looking for a visual analog of partner completion and satisfaction that most women get by default, and typically with little to no effort on their part.
So the squirts, the farts, the queefs, the twitches, all the little involuntary signs the body is being pleasured in ways she cannot or will not express openly are probably going to register in a lot of men's minds as the goal, and that's long before porn gets involved.