Mainly, because of the number of people. Look at earth's surface on any type of map. You'll see human activity virtually everywhere. Fly across the US, and out your window you'll see most of the surface converted to industrial food production. Places like NYC, LA, and Chicago exist. "Suburbs" are a thing.

You're somewhat newer, so it may seem more normal. It's just the 'new normal', which would be a literal hell to people from less overpopulated times.

I only do this half-hearted rant on occasion, because it seems clear that humans are destined by character to self-destruct. We would face none of our current problems with a sustainable population level, but we're unable to self-regulate. Our agenda as a species appears to be Cancerous growth at all costs.

While I was too young to appreciate it, a world with fewer than 3 billion people was pretty nice, comparatively. Looking back from current year, it's almost like we've entered the Christian tribulation.