If your sentiment is the most common, including a modem in MacBooks makes only sense for the tiniest of tiniest of user slice, and with Apple barely cattering to pro users, I can't imagine them investing further to solve a problem that isn't as simple as just slapping an extra part in the machine (which they traditionally hate).

On my side it was 90% there, a bit lagging to connect and totally failing from time to time , once in a week perhaps, but workable otherwise. The argument on the podcast was for having a 100% great solution like it does on the iPad, assuming an internal modem on macos would rainbows and ponnies.