> and I ran a 1600x1200 desktop with 24-bit color

> What has changed? Why do I need 10x the RAM to open a handful of terminals and a text editor?

It’s not a factor of ten, but a 4K monitor has about four times as many pixels. Cached font bitmaps scale with that, photos take more memory, etc.

> When Windows 2000 came out

In those times, when part of a window became uncovered, the OS would ask the application to redraw that part. Nowadays, the OS knows what’s there because it keeps the pixels around, so it can bitblit the pixels in.

Again, not a factor of ten, but it contributes.

The number of background processes likely also increased, and chances are you used to run fewer applications at the same time. Your handful of terminals may be a bit fuller now than it was back then.

Neither of those really explain why you need gigabytes of RAM nowadays, though, but they didn’t explain why Windows 2000 needed whatever it needed at its time, either.

The main real reason is “because we can afford to”.