I wanted to ask a networking security question about open or public WiFi. This question is not a duplicate of Why isn't open WiFi encrypted?
Reading about cellular networks I found out that cellular data is uniquely encrypted for each user between the network/base-station and him with the help of the SIM card. Why does't something similar happen in public/open WiFi (taking into consideration an analogy of the base station with the router and the SIM card with a NIC card perhaps)?
This would allow encryption for every single user and avoid the problem of insecurity in public/open WiFi where there is no password (no encryption-in data link layer at least, not referring to https which is application layer) or a common password (making the encryption useless to someone that knows it and is seating in the nearby coffee shop sniffing packets).