Most cellular carriers offer unlimited on-device data plans, but they cap data for tethering. Integrating an LTE modem into a laptop essentially requires a mobile data plan with unlimited tethering - which, AFAIK, doesn’t exist at the moment. I’m not sure why.
I've always heard that patent disputes were at the root of the lack of a modem option. Apple had a prototype MacBook Pro back in the early Intel days IIRC but it was never released.
Maybe if Apple ever gets their in-house modems working, we'll see them on all of the product lines, but until then, it's a niche use case that likely isn't causing them to lose a ton of sales.
I understand that. My point is that I think an LTE modem in a laptop might reasonably use far more data than an LTE modem in a phone or tablet. Most people who download and/or upload very large files do so on their computer rather than their mobile devices.
There is no reason macOS cannot have some option for throttling usage by background updates when connected over LTE. iPads have an LTE option.
That carriers have not figured out how to charge me by the byte over all my devices instead of per device is really not a big issue to me. I would like to pay for an LTE modem and the necessary bandwidth.
My intuition is that when Apple has their own LTE modem and is not dependent on Qualcomm, a MacBook Pro will have an option similar to that for Dell power users.