Sure you could just offload the problem to the operating system via something like GStreamer but that just moves the target, it doesn't eliminate it. It just means anyone who distributes your OS gets into trouble rather than your browser distributor.
This is about eliminating the possibility of submarine patents for an essential feature like video, not just moving the target around.
Open Solaris tries to get around this, by getting you to pay for the codec after install.
Of course not paying is the ideal outcome, for most consumers.
Surely it's not hard to make an operating system and browser that makes it almost transparent to install a codec or bit of software.
I agree, get gstreamer or something else to work seamlessly. And at the same time, give me the ability to turn the damn thing off. I can already imagine, the state of web pages to come, it will be like a license to put video adds all over my webpage, and drag my cpu into hades.
It won't cause them any sort of enlightenment, but it will make me feel a bit better.