I think Unity also caters to indie developers with new game ideas, as well as to rapid prototypers. (The two often overlap.) Would we have gotten games as cool and varied as Receiver[1], Broforce[2] and Hearthstone with UE? I kinda doubt it.
[1] http://store.steampowered.com/app/234190/
[2] http://store.steampowered.com/app/274190/