> I speculate [fork] isn't common, or at least it isn't required for ordinary desktop apps.

From a science perspective, the ability to fork is really convenient for parallel processing. Load some data and then fork a pool of worker processes, and they can all read almost free copies of that data. This is much easier than setting up shared memory. It's a bigger deal on an HPC machine with 128 cores than a laptop with 8 cores, but even on a laptop it's a significant point in favour of Linux.

Getting rid of it in Linux would also be going against Linus' rule that the kernel never breaks userspace.