Where is that the case? Middle click copies the selection and right click pastes on every terminal emulator I use.
What terminals have middle-click-to-copy, right-click-to-paste? Sounds alien to me.
[0] https://en.wikipedia.org/wiki/X_Window_selection#Clipboard
CMD on Windows, default PuTTy settings, WSL as well. I honestly haven't used GUIs on native Linux environments much, and when I have I must have changed the terminal emulator settings.
I mostly used this to copy paste from a terminal into a COTS GUI tool, or from that tool into the OpenOffice (or maybe LibreOffice, I don't recall) spreadsheet program whatever that's called.
Honestly it was incredibly useful and probably saved me collective hours over the few years I worked there
Obviously this thread is about terminals, but the functionality does exist in some places