What you say is true.
It is also true of tethering, which is quite popular.
Now, I can tether my phone to my laptop. Indeed I did so fairly often, before global house arrest.
But this is true of my iPad as well, and I opted for the cellular model instead. I'm glad I did, it's a better experience, hands down, especially when I'm traveling and want to conserve my phone's charge rather than burn it at maximum.
But if you felt differently, Apple sells a WiFi only iPad, you could simply not pay the extra for the cellular model when checking out. This would almost certainly be true for this imaginary Macbook as well.
I wouldn't buy it at all, I'm a professional developer with mild presbyopia, and purchased the standard-fancy model of the 16". But if I were an incoming freshman again? Bet I'd be pleading with my parents to get the cellular model.
Unlike a touchscreen, an LTE modem doesn't demand any changes to a desktop operating system to provide a good user experience. Again, tethering. Cell bandwidth gets cheaper every year.