Yes, commiters want to see their work in the kernel ASAP. Still there is a reason for this merge window to speed up the general releases of new kernels. This is: many contributors are able to get their code into the kernel in this small merge window, why not all? If you look at the last three kernel releases you will see that the release of the final version was delayed due to regressions in late merges. Basically all of the rest was working nicely, there were just extra problems introduced by later merges. Without those the kernel would probably have been out at least two weeks, maybe even four weeks earlier.
Adhering the rules will help and reward other contributors to the kernel by a faster release cycle. Since there are not only graphic card manufacturers working on the kernel, but eg manufacturers of embedded systems and the like. The kernel is not only about 3D graphics and their acceleration but also about all the other stuff the OS should offer like drivers for your mass storage devices.