AMD's been adding more PCIe lanes across their hardware lineup than Intel has to be sure, but EPYC is server-class stuff with 64 cores to a chip. The Ryzen 2 2700X only has 20 lanes for 8 cores.
I spent significantly more for the CPU on a personal build a few years ago because I needed 40 lanes instead of 24. I'm all for AMD messing with it.
That, and the eye-popping multithreaded performance for encoding.
And Intel got away with it because they had no competition. Monopolies are always very, very bad for consumers.
I'm hoping Ryzen 3rd gen bumps the lane count a bit more, otherwise Threadripper's 64 lanes look mighty nice...
I'm surprised they don't come with more, especially many of the current ones come with 2-3 x16 slots, AND 2-3 M2s.. Both Intel and AMD have been adding more cores recently. Plus, if you're doing any GPU-based rendering, they're going to simultaneously move data back and forth from NVMe to the GPU's memory. But it grabs a headline and most synthetic benchmarks will only test RAM, graphics and storage in isolation - sneaky!
Games definitely don't do this at all, which is the primary market for a discreet GPU in these consumer platforms.
When they do stream in assets they do so slowly & in a controlled, rationed amount to minimize impact on FPS. They are far from being PCI-E bandwidth limited. That's kind of why you see almost no FPS drop at all when restricting GPUs to x8 bandwidth, even.
If you're doing something more workstation-y or custom, that'd be when AMD & Intel would point you at the HEDT platforms which have more than 16-20 lanes.
I'd imaging a workload like that or other HPC-compute workloads where the data set just doesn't fit in VRAM would certainly prefer more PCI-E lanes.
I think that'd usually be considered using the wrong hardware for the job but if you're just messing around as part of a hobby you're obviously not buying the $7000 Radeon Pro SSG, either.
In raytracing complex scenes can exceed your VRAM so if you don't want to fall back to CPU tracing you need a renderer that can swap parts of the BVH in and out on demand.