Actually the analogy is good. Having a physical token is very messy from a UX perspective. A menu is just as easy: If i want to use carrier A, i select carrier A in the menu, if i want to use carrier B, i select carrier B in the menu. This is what i do every day with my WiFi-network on my laptop....
Your µSD-comparison is what doesn't make sense. An SD-card can contain several gigabytes of data that would take hours to transfer to the phone. A SIM-card probably has a small key on maybe a few kilobytes that can be transfered and stored by any more or less modern communication-method, wired or not, within a few seconds.
But from a security perspective SIM is a much better solution because once you make the key transferable by software it will be much easier to steal an identity.
Your µSD-comparison is what doesn't make sense. An SD-card can contain several gigabytes of data that would take hours to transfer to the phone. A SIM-card probably has a small key on maybe a few kilobytes that can be transfered and stored by any more or less modern communication-method, wired or not, within a few seconds.
But from a security perspective SIM is a much better solution because once you make the key transferable by software it will be much easier to steal an identity.