Today, I can connect to a person hot-spot or coffee shop wifi, but that's Another Step and many wifi hotspots like to boot me if I close the lid, even for a short time. Having a laptop that's seamlessly connected at all times would be seriously cool. Harder to lose when always connected (Find My), too.
Sure - just google "<vendor> 5G laptop" to find for example https://www.dell.com/en-us/shop/dell-laptops/sr/laptops/5g-m...
It's often found on business laptops given to service engineers and sales people, who spend a lot of time on the road.
I think the two largest blockers to WWAN on laptops are: handling of SIM card, and complexity of setting up wireless contracts. Which aren't _that_ complex, but scary enough to make target demographic hesitate. Apple WWAN would use eSIM, and certainly an easy signup through an included assistant app that could change the equation.
Still pretty common in a lot of business focused models. And I believe some big corps with a lot of travel & security concerns still have custom models made for them with specific cell systems built in and centrally administered. Saves ever having to answer the question : should I connect to this network....