A prototype is a demo. A product is a promise.
Prototyping tools are genuinely good at what they do. They're built to prove an idea quickly, and they do. The gap isn't that the tool is bad. The gap is that nobody asked it for the things a live product needs, because a demo doesn't need them.
Nothing is specified
The behaviour lives in the screens and in your head. Nobody wrote down what's supposed to happen at the edges, so nobody can tell when it's wrong.
Nothing is tested
Every change is a gamble. Fixing one thing quietly breaks another, and you find out from a user rather than from a build.
Nothing is secured
Keys in the client, no real auth boundary, data anyone can read. It doesn't matter on a demo. It matters the day you have someone else's data in it.
Nobody runs it
No monitoring, no backups, no one on call. Prototypes don't have a 3am. Products do.
It can't be handed over
Generated code with no structure and no documentation is hard for the next engineer, or the next model, to pick up safely.
It doesn't connect
Real products talk to payments, identity, email, and the systems you already run. That's where prototype scaffolding usually stops.