Anybody who believes the GPL was invented to coerce users into sending patches ought to have their head examined.
It hasn't won in the market place -- and it won't -- primarily due to the fact that the coupling between funding and licensing is so indirect -- it's very difficult to earn a high margin on writing GPL licensed code, and most revenue models require an indirect and complex approach to earning money from the software without charging directly for the software itself.
(Yes, you can charge for GPL software. No, that's not a sustainable business model. No, RedHat is not a counter-example. RedHat charges for support and their trademarks, not the software itself, and in doing so appeals to a very specific niche enterprise market.)