I've never understood this behaviour. Is it because they don't want to send any official communication stating that they don't want to/cannot match your compensation request? Is it just bad blood? No idea.
90% of the time it's just because people are busy and have a god-awful amount of crap on their plate. They figure your interest will time out gracefully.
No idea, but it is obviously rude, but also in the current “lack of engineering talent” climate a very bad business practice. I have worked for a couple of FAANG and other large companies, and been rejected by many more. But they have always responded after the interview process began.