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!"