Do not confuse the ability to use a phone or laptop with technical knowledge. People know how to use apps, but all the technical stuff is abstracted away.
I'm pretty technical (As is nearly everyone on HN), and I have no idea where my photos are stored on my Android's file system. I have no idea where the APKs are for all my installed apps, or where their saved data sits.
I was surprised the other day that my photos weren't being stored locally on my iphone, but in the cloud. I finally found a setting that turned that "feature" off. Obviously, it had defaulted to "on".
But if _everything_ is always saved on the card, then you don't need the technical knowledge. Removing the card would leave the phone in a "factory clean" condition.
If everything is on the SD card (as in: it won't work w/o the card inserted), then it will have to come with a card pre-installed. In that case, the average user won't even realize there's a removable card. It's turtles all the way down.
The card could come separately from the phone in the same box. Phone boots up off the OS on internal storage, and the intro wizard says "Now insert your SD card, which is where your personal data will be stored." Done.
But if the phone doesn't come with a card pre-installed, people are going to complain that it doesn't work, or that they didn't know they had to purchase a card.
Unless it comes with a card, but the card is not inserted, so the user has to do it before booting up the phone
I'm pretty technical (As is nearly everyone on HN), and I have no idea where my photos are stored on my Android's file system. I have no idea where the APKs are for all my installed apps, or where their saved data sits.