It's still a habit of mine. I have 2 external monitors on my desk connected to my laptop. One of them is a bit older LCD, but still functions well for purpose. It has a fun little quirk where when it first turns on there are a few vertical lines of a solid color until it has "warmed up" and the lines disappear after a few minutes. By using a screen saver when I get up and lock the screen, I don't have to wait for that screen to warm back up. At night, it does eventually turn off the screen saver after my timeout, but at least it's not every time I return to the desk.

Also, from a time long ago in a galaxy far away where we had production CRTs that were color calibrated, we would not turn them off either. They had a saver mode as well by running a not quite black signal to them, but not enough to burn in phosphors. It was even meant to "even" out some of them.

So because I'm that old that has used CRTs for such a long part of my life, screen savers will always be just part of the routine.

As much as I disliked open plan offices, I did enjoy trolling my coworkers with fake blue screen of death and kernel panic screensavers. Windows 95 "Pipes" also got a lot of nostalgic shoutouts when I used that for a while.

I like the newest mac update shore video, Tahoe I think with the liquid glass

it's a combination of people seeking aesthetic (imo), and naturally, preventing an oled, plasma, or crt from burn-in