Earlier quoted context omitted.
They literally have one click pairing to the Wifi hotspot on an iPhone or iPad logged in to the same iCloud account. Everyone has a phone. Why increase the BOM?
This logic doesn't hold - the same is true of an iPad. To quote you, "Everyone has a phone. Why increase the BOM?" - if it's ok to include cost of a modem for an iPad, it's ok for a MacBook Pro too.
This exactly.
The iPad is already like a smaller MacBook without a built-in keyboard that runs iPadOS.