Linux has historically also done this. Unused RAM is wasted RAM. So in goes the cache.

(Not sure you read the post, but it doesn’t come off very pro-filling RAM!)

Anyway, the downside of filling RAM aggressively is that it convinces users that their RAM is in very short supply, hence causing them to make issues/reddit posts/forum posts complaining about the RAM usage of even fairly conservative programs. I can’t totally blame them - if your memory only has a gigabyte free at startup, and $program uses a gigabyte and a half under heavy load, it’s natural to worry that something is going to go wrong if you open it!

Of course it doesn’t work that way, especially on modern machines with fast SSD swapping, and the memory filled at startup is mostly purgeable cache data. Doesn’t stop the complaints!

This, and also that it hides away valid complaints about actual memory leaks. I can't remember the number of times I complained about Firefox leaking memory, and got brushed away as "that's just how Linux works, it fills your RAM for cache". Well, if it's just cache, why is it thrashing my PC everytime it fills up? This even led me to misunderstanding about how kswapd0 works, and prompted me to ask how to "disable swap" because the OOM won't fire as it used to in the olden days.

After some time, work forced me to switch back to Windows, and now everytime I see complaints about how Windows gobbles up RAM, I just say to myself, "Hah, that's how Linux works too!"