Well, I get very wet if excitated and I mean very wet.
But no, I never squirted in my life.
Such thing indeed exists, but very few women are able to do it.
In most porn movies is a hoax, done in the movies with little liquid pockets hidden inside the vagina. Sometimes in real life, some are faking it with just a small amount of pee mixed with the sexual wetness that gives it that mater and denser colour.
Why most girls cannot do it?
Because the sensation right before squirting is something similar with wanting to pee and here girls with any mental blockage in regard to watersport, will immediately stop.
Amy, I can vouch for the fact that it is not pee, I don't know about porn movies and how they do it but it is a real thing with some women.
And maybe some others are never stimulated well enough to get there
luckily I am not in this category as I can get excited watching a wall if I want to
PS> Edited to add:
Apparently there is some other category of women that are not able to squirt, have a look below.
"During gestation the male and female start with the same tissues, it's only after sex differentiation at about 40 days that the genitals begin to look different in the male and female fetus. The tissue which becomes the prostate in the male does not just disappear in the female, it becomes the paraurethral glands which surround the urethra. Based on postmortem dissections, we know that the amount of glandular tissue varies from woman to woman, and some women have no discernible glandular tissue in their G-spot.
In some women the paraurethral glands produce fluid when the woman is highly aroused. Because the paraurethral glands open into the urethra, the muscle contractions of orgasm force this fluid into the urethra, and out of the body, creating an ejaculation of sorts. There are those who claim all women can "learn" how to ejaculate, but biology suggests otherwise; women who don't have any glandular tissue can't produce anything to ejaculate. Other woman may produce such a small amount of fluid that it's not noticed when mixed in with the other fluids that sex produces. Small amounts of fluid might not "squirt" out, but rather drip out after orgasm, much as semen does when a man has an almost-dry climax. It's also possible that the fluid may leak out before orgasm; men have a sphincter (valve) "downstream" of the prostate that keeps fluid from leaking, but women have no such sphincter. It has also been speculated that in some women the fluid is sent "upstream" and into the bladder."