I'd say, judging from the looks of it, that Morrus is spot on.
Some folks I'm sure want a complete lockdown on third parties' use of IP. I mean, in theory, there's tons of licensing money just laying around!
Others are
OGL fans. Or at least think D&D benefits from being an open-ish platform.
What we have is somewhere between it - where the only reasonable third-party products are modules and - to a lesser extent - settings.
-O