Right after a comment I realized #3 or perhaps #1
Most popular sites won't adopt the simpler web even if they can afford to do 2 version of their site, even if users like it. Because the lighter web most certainly will be worse for ads and tracking.
Each of the two standards might not receive enough attention on their own, but they complement each other: getting rid of the necessity of ads means going lite is an option for website owners, and the lite web will allow for many different lite web clients (that might finance itself through in-app ads shown to the user). In combination these two might overcome some threshold and gain traction!