Sure, but those predecessors like MPEG-1 were patented too. And if they would've been created and shared anyway, why didn't Xiph and Ogg exist before MPEG? And even had they been created, would there have been the same incentive to do cross-vendor standardization? Without the patent, the monetization incentive is to keep everything under your own roof.
I'm not talking about MPEG-1. "mplayer -vc help" outputs 393 different video codecs. There's no way that every single one of them is unique and uniquely patentable, or that every one of those formats was created because of patents. The proliferation of codecs indicates that, if someone needed a video codec and a suitable one did not exist, they would make one. As for the incentive to standardize, the incentive would be the same as any other free market: interoperability allows your products to be used instead of someone else's.
Xiph and Ogg didn't exist before MPEG because Monty wasn't around to start them. Ogg Vorbis development was started in 1993, but was finished and popularized in response to an unexpected crackdown by Fraunhofer on implementations of the ISO MPEG standard.
