[mainpassathome]

it doesn’t not support it, it doesn’t set this unexpected behaviour as default

[Aardwolf]

Whether it's unexpected or not depends on the user, you could as well say ctrl+v pasting in windows is unexpected if you don't know this shortcut. Middle click paste in linux is a standard feature this OS has always had

[macNchz]

The problem being that middle click does other stuff, like opening links in new browser tabs.

[midasuni]

Middle click paste is very much expected - it’s been standard for at least a quarter of a century