It does do something though, it paste directly from the latest info from the clipboard XD. So, if you highlight something, then middle click somewhere else(not just a browser, basically system wide) it will paste what ya highlighted.
default settings, everything on GNU/Linux can be customized. Getting done to change the default is always a struggle. For example it’s been decades that in GNUDE the middle button click has been paste, so while it may seem dumb to you that it does that, it’s user base expects that to be the default.
But as you’ve already found in this thread in a meme community, one of the best ways to learn how to customize your system the way you want is to claim in a Linux forum that Linux can’t do such and such.