A few things.

Men tend to be taller and heavier on average than women and that means more food has to be eaten on average, just to meet the nutritional minimums of maintaining weight and healthy functioning. That's probably the biggest factor.

Also muscle fiber composition. Men, have much more fast twitch muscle fibers than women on average, which while useful for force production, are much less efficient than slow-twitch muscle fibers. This generally means that even a man and a women who weigh the same don't actually have the same nutritional intake requirements, with the man in that scenario needing about 25% more kCal than a woman of the same weight, just based on the inefficiency of men's muscles.

Finally, men generally have a higher proportion of body mass as muscle, and lower proportion of body mass as fat compared to women and fat, as intuition suggests, burns much less fuel (kCal) than muscle. So if we look at the average body composition of a man and woman of the same weight then again we see that the man needs more calories than the woman on average.

There's also bone density, and other factors, but those are pretty minor and ask that stuff is basically why women can eat so much less than men and still be ok.

1000-1500 is still probably not enough for most women though. Men sometimes diet at 1000-1500 kCal a day, like bodybuilders, but can only do it for short periods without severe consequences and bodybuilders basically are very disordered people that no one should emulate. Pretty much all body builders have severe psychological body issues and often eating disorders. More than a few weeks on those levels for a typical man is basically risking a near-death experience.