It wouldn't be pointless for me. I quite often use my iPhone to provide an Internet connection for my MacBook Pro. I wish it were more reliable and didn't consume so much battery. Dell and other laptop vendors have been embedding cellular modems in laptops for a long time. Apple manages to put one in a watch and every other device.

It appears that the Qualcomm license problems are the only impediment to Apple putting an LTE modem into a bigger device.

They pretty much only exist in business laptops because in that context it can be useful to issue someone a field laptop with a SIM in it, and it doesn't really mean much for cost on a large corporate data plan.

What if you want to save battery life on your phone while you're on the go? I imagine having LTE modem in the machine must be a less laggy experience as well.