The use of "himself" in this sentence is emphatic, and serves to emphasise the fact that "Bob, and Bob in particular".
The emphatic pronoun "himself" can be omitted without changing the core meaning of the sentence. But as with other forms of emphasis, often the reason for the sentence is to emphasise something, so removing the emphasis changes the intent or purpose of the sentence.
In this case it is used correctly to mean "Bob (and not his parents, or his friends etc)"
It could also be expressed as "If Bob doesn't want to be a doctor himself."