No, it doesn't have to be this way 100%. For example, why can't the Macbook have a simcard reader? It's fairly natural, other companies offer laptops with simcard readers. This is Apple just wanting you to tether your iPhone or buy an iPad, which comes with compromises (not only more expensive for you to own them all). The natural choice would be to simply have a simcard reader in the Macbook...
Or the iPad that is mentioned as a replacement for a computer, but really isn't. They deliberately implement bad file management on the iPad, as an example. Or bad handling of external screens. Or no porting of important MacOS apps.
They are simply desperate to differentiate them, even if leads to a worse product. Even if they sit there in their design meetings and talk like... "yeah, we actually have solved all this stuff in MacOS, we could just port it to the iPad... but then maybe people would start to buy less MacBooks because they actually feel the iPad is a good replacement...".
It must suck to sit and develop such obviously castrated products.