carrier authentication is huge! do you want someone to be able to subscribe to a network with your phone number? receive your calls? texts? or call or text as if they are you? yes the sim has little relevance to device security for most smartphones. contacts on sim are a great example of supporting legacy features for BC only. but the network is still very important to secure.

sims are used for more than just phones. the chip on your credit card is a Secure Element. the chip in your passport is too. these are some of the most physically and technically secure pieces of hardware ever made