Read and write speeds. Sure, there are 100+GB Sd cards but the read and write speed, unless it's a special proprietary chip, won't be fast enough to run games that need that much data. At least that's what I've been researching because I had the same questions you have.
I don't think Nintendo is aiming to appeal to developers who need such absurd amounts of data (mostly taken up by models, textures, sound and shader data. And any pre rendered films included. I think Switch is going to appeal to most japanese 3rd party developers and a handful of western developers (much like the 3DS). And going by the content on the 3DS with a max of 8GB, games that require more than 64 GB aren't going to be ideal or necessary for the switch.
That's just how I feel about it. Switch will accommodate a great amount of data no doubt, but for what the Switch is, trying to accommodate a game that is as huge as infinite warfare (130+GB, not counting patches), isn't ideal.







