Ah, the wonderful internet where everyone thinks every product revolves around them!
SD cards can now run at 90MB/s (very reasonably priced, large, usable for many purposes) or ~300MB/s (expensive, max out at 256GB right now but fast). Why does this matter?
Because it means that you can buy a Mac with smaller amounts of the max-performance flash that Apple provides, and make up the difference with an SD card that sits permanently in the SD slot. Run your mac off 256GB or so, and put your movies and music on a 512GB or 1TB SD card.
It works well, it's very convenient for many use cases. Yes, your movies and music can only be accessed at a "measly" 90MB/s or so rather than the 3GB/s of an internal drive. If that's a problem for you, you're probably using your movies and music in a highly unorthodox fashion...