Microsoft is building its own SIM card for Windows
theverge.com
theverge.com
That said, does anyone know any universal 3G/4G/LTE dongle? Almost everything I found is made exclusive to a specific carrier. How come cheap tablets come with a universal data capability and yet no usb dongles?
The Microsoft "special" sim card is presumably a standard multi-MVNO sim card with (presumably) some nice app for buying service. Similar to Apple SIM or Google Fi.
It's nice to have for people who and aren't carrying around SIM cards to swap around. (Maybe they don't know what a SIM card is, or maybe they haven't had time to burn 2 hours in a mobile provider shop to get one). They can buy a device, turn it on, and the app walks them through buying data automatically so everything "just works".
AT&T will lock your physical SIM if you ever use their service, but with anyone else you can jump from provider to provider on the same device at will.