That's really absurd. People make food for friends and build everything from furniture to vehicles for fun in their garages without complying with any professional standards or laws all the time. How many people on Hackaday or any DIY site have ISO compliant or OSHA inspected labs? Existing regulations are not stopping the maker space scene.

You can play car mechanics as self taught builder, the moment the car needs to hit the road, it must certificy road regulations.

Not being a Mechanical Engineers doesn't prevent building the car and putting it on the road, provided the regulations are met.

And if something happens to someone else with that car, the one building it is also liabiable, provided it was caused by a construction error.

However not having an Engineering license doesn't forbid it to being built.

Many programmers are factory workers, plugging software libraries, that is why open spaces are organized like the mills from industrial age, or the offshoring sweet shops exist.