The point of the passport is that information in there is readable easily. I can easily check my visa state as can the cop checking me somewhere. Also the passport can be checked by a porential employer to verify my integration state which might include a working permission. Also mind that in many countries of the world (i.e. in many African countries) technology is of limited availability. Any digital form would require data exchange formats and protocols. Printing/stamping/sticking can be done everywhere easily and the protocol "paper pages of size 125 mm × 88 mm" is trivial.

The thing you describe essentially also exists in many countries as a ID already, which I.e. can be enough for EU citizens to travel within the EU.