Is it, though? I really don't think it has. There's still plenty of GPL-licensed software out there; most of the software I run on my laptop is still GPL, for example (the main notable exception being Firefox).
I think perhaps there's just a lot more open source out there these days than there was 10 years ago. A good amount of it was started by or sponsored by corporations, and sadly those types of entities are less likely to use the GPL.
But that's fine, no skin off anyone else's back.