Why does he want to eat green fish?       It costs less money.....

Now, just as before we can also say:
Why doesn't he want to eat green fish?  
(Wh + DOESN'T/DON'T +  S + WANT + TO + V1)
 Why (Wh) doesn't (DOESN'T/DON'T) he (S) want (WANT) to (TO) eat (V1) green fish? 

Now, as long as we have the green fish fresh in your mind,  let's see another thing that happens with (TO + V1).  Up to now, one person is the subject. So here is what happens when:
Karl wants you to eat his green fish.
Karl (S) wants (WANT/WANTS) you (S2) to (TO) eat (V1) his green fish.

OMG! (S + WANT/WANTS + S2 + TO + V1)
There are two subjects in that sentence! (...And you are one of them!)

First, look at the difference:
Karl wants to eat his green fish.
Karl wants (you) to eat his green fish.

BIG difference.

So try this one with Mary as (S1):
to drive does wants eating Mary Karl
____ ____ ____ ____ ____ her car.

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