> How would you know? You have never used such a system because it doesn't exist
I have, it does, it's called Oberon, it was glorious.
Copying text from UI elements was also never an issue for me in GTK2 (can't speak for 3, haven't used it much), it was great (although I admit I don't know if there were a few places in the system where I couldn't copy text, it may not have been 100% the case).
When I'm working in terminal apps (more often than you can likely imagine) on Linux I can also expect to copy text everywhere, it's great.
I'd encourage you to use a diversity of computing systems, it'll broaden your perspective and imagination and sense of possibilities :)