Because that's all they put on the CPUs. You still can't seem to put together any sort of specific hypothetical use case where it's going to actually pose a noticeable limit to yourself though. Or even, how about some benchmarks showing where it's a real limit vs. the Intel CPUs with more lanes?
I just want to use M.2s and the fully populated PCIe slots at the same time. Then I would believe it.
I was hoping to have the laptop to learn more of Windows 10 first though.