> People can drive a car without an expert

Not every person can drive a car.

> but they can't build a car.

Not every person is unable to build a car.

Eg: my father, born 1935, still alive, has built double axle trailers, cars and vehicles that work, medical caravans for St Johns Ambulance, ...

His education was six years of primary school and these were all "side projects" for himself or for his community.

> you still need a decent level of knowledge in either field

and the barrier to picking up sufficient knowledge to safely create software, cars, even ground effect flying boats isn't that high for normal human beings .. although it does require a certain can do attitude.