Hey, if rubber domes do fine for you, then by all means no reason to spend extra money when you are content
Someone like myself though that either types too fast on those rubber dome boards or plays competitive FPS games like Shootmania, quake live, csgo, etc. etc. I tend to find my hand movements are "too fast" for the keyboards to keep up, as such I made my move to mechanical. If the majority of your gaming belongs in non-fps categories, much less non-competitive categories, or if you aren't a typist, I really see no reason to move to mechanical.
For me it was both the feel and the ability to not be stuck with 2 or 3 keys being pressed locking out any others. My main reasons for going mech at least. But the feel of it... no way to describe it if you have not lain your hands upon a mechanical board.