1. Most of the federal land agencies have been underfunded and understaffed for decades now. NPS, BLM, USFS. This is on purpose.
2. 2005 onward - the explosion of people using the outdoors.
3. Millions of boomers retiring and RVing post Covid.

Avoid the summer or get lucky. Even the shoulder seasons are stupid busy. Glacier was packed well after Labor Day, and before Memorial Day.

I'm more likely to do dispersed camping these days, but people like bathrooms.

Edit to add: Van lifers. Lots and lots of people in the last 7-10 years permanently traveling, and a large uptick post Covid with remote work.

There just isn't room for everyone, and of course the bots.