All the other brands went along

The desktop equivalent is "What happened to all my PCIe expansion slots?!"

(Note: processor PCIe lane count has gone up, used to be like 16 from CPU, 4 from chipset, since a GPU didn't need an x1x6 in terms of bandwidth - see SLI/crossfire. These days, it's just that many lanes go to M.2, with each using up to 4 lanes - vs having 6 SATA driven off the chooser)