Welcome to the forum
The Surface 3 came out with LTE capability, some time after the initial release. I suspect that if things go well with those sales they will also make an LTE version of the SP4 M3.
TBH I would much rather get a portable hotspot I could use with multiple devices rather than purchase anything other than a phone for mobile data and get into yet another contract.
I'll never understand that must-have, either; it's a
computer not a cell phone.
My company provides us with Verizon Mi-Fi devices, which we use primarily with our corporate laptops. No need for IT to search for and establish a special LTE-equipped laptop model as the standard; rather, just give us the best laptop you can and when we need mobile connectivity, we'll use the Mi-Fi device.
I'll go one step further: My company actually provides
multiple brands of Mi-Fi devices. At one particular customer location, for example, the T-Mobile service was practically unusable, so we all ended up using the Verizon Mi-Fi instead. I'd rather have this flexibility for a portable computer rather than have (more-than-likely) an inferior laptop with built-in/fixed LTE capabilities.