Plenty of smartphones have eSIM support to enable cell service without a conventional SIM card, but only for one line — you still need a card if you need two lines. That won't be an issue with iPhones from now on. 9to5Macobserved the iPhone 13 and 13 Pro both include Apple's first support for dual eSIMs. In theory, you can use multi-line support without picking up a physical SIM.
There's still nano-SIM card support if you need it. Apple makes no mention of using the nano-SIM slot alongside the dual eSIMs. We've asked Apple for comment, but you shouldn't expect three-line support at this stage.
The usual caveats apply. Some carriers aren't fond of eSIMs and might limit your ability to switch carriers. Others might not support eSIMs or even disable them in versions sold by the network. In the right circumstances, though, it could be ideal for international travel, business lines or prepaid service. You might never need to visit a carrier store or wait for a SIM in the mail.