We use it and like it because we are trying a lot of models per unit time. And we want to change them, slide in new data, transfer weights, and others things like that, without headaches.

So the real reason is for internal efficiency for model prototyping, or more direct: results per human-hour. If we have to spend time in troubleshooting land, then we're losing our Startup Competitive Advantage™ in DL (the ability to move fast).