Dunno where to sit on this one- but I agree with the points that some people dont have the expertise.

In all fairness tho- u can learn them. For example- I can change the gearbox on my car and clutch and also pretty much all of the major components.

The knowledge I dont have is putting the engine together properly or how to weld or how to set the components up- Thats why I pay people to do it or ask for their help.

J