Why do women just stop replying?

There’s no one answer, of course. It can be a romantic context or a strictly platonic one, but sometimes a woman will just stop answering messages or phone calls, leaving me to guess why on earth, even when I don’t see any reason for it. I’ve been told that this is typical behavior – that women will be uncomfortable explaining why they want to break off contact. But… why? Isn’t it more uncomfortable to have someone wondering and trying to figure it out and asking, etc?

So, please just dump a bunch of random examples on me. Why have you done this to people, why have others done it, why have people finally said they did it, etc.