If doctors can't treat themselves then what hope to they have to treat others?

If (most) humans can't build passenger aircraft what hope to they have to let others build aircraft for them?

see the flaw?

Politicians are supposed to be representatives of the people and they are supposed to be competent and informed enough to make decisions about public goods that the average joe is too ignorant and incompetent to make.  Not saying that this is always true in practice though...