> I wonder why there was never a standardized PCIE 'card' format? Seems like the perfect thing for extra storage with NVME being so common these days.
The best thing about standards is that there are so many of them to choose from. The closest analogue is the ExpressCard (https://en.wikipedia.org/wiki/ExpressCard), but there's also the internal-only M.2 (https://en.wikipedia.org/wiki/M.2), which is the most common non-server format for NVMe; mini-PCIe (similar to M.2, used mostly for wireless); SD express (SD cards, but with PCIe); and CFexpress (CompactFlash cards, but with PCIe).