I think this is a case of "that's how it's always been done". My understanding is that it's done this way so that there's a consistent experience installing so

I think this is a case of "that's how it's always been done". My understanding is that it's done this way so that there's a consistent experience installing software from a CD/DVD or from a download online. But I think you're right, Apple should've rethought the software installation process the moment they dropped the optical drive from their computers.