Just wondering my Apple don't give the option to build Macbook's with built in SIM cards or at least some card trays like the Cellular iPads? Would be perfect for those on the go all the time to save having to tethering.
Sometime my iP13 takes 4/5 attempts to connect as a BT Hotspot...
The issue is not 'built-in SIM cards'; the issue is including a cellular modem.
This is one of those great mysteries. With Apple Silicon and eSIM, it would be easy to include cellular support if they wanted to. Much easier than in Intel-land with physical SIM. All the engineering to connect an M2 to a cellular modem has already been done for the cellular M2 iPads!
But... the other thing they may be looking at is sales data from Windows land. Dell/Lenovo/HP have offered cellular options on their business laptops for close to 20 years. For a time, they even shipped all models of some business laptops with the SIM card slot, the cable to it, etc, so the only thing you needed to add was the cellular modem card itself. But inventory configurations sold through VARs like CDW rarely have the cellular option, etc, and so I think very, very few people actually buy the cellular-capable Windows laptops. Apple may be looking at those numbers and saying 'our take rate would be even lower, it's not worth it.' Doesn't help that while Dell/Lenovo/HP can offer a single mPCI/mPCIe/M.2 card model across an entire year or two or three of their business laptop lineup, Apple would be building it into the logic board, therefore they would
double the number of logic board variants. That's a lot of supply chain complexity especially when the move to soldered RAM/storage/etc has already caused a huge increase in the number of logic board variants.
The other thing to note is the experience with the iPads. It's very unusual that Apple has offered every configuration of iPad with a cellular option. Some people know about cellular iPads and absolutely love them, but the impression I get (speaking as someone who orders and hands out cellular-capable models exclusively in a workplace) is that most iPad buyers only know about the wifi option and don't even think about cellular when buying. Who knows what the take rate on cellular iPads is.