modal verbs - "X won't Y" (able/willing) vs. "X doesn't Y"

In the preschooler series "Peppa Pig" I met the following two sentences:

1. George runs as fast as he can but the kite won't fly.


2. Peppa runs as fast as she can but the kite still won't fly.

I understand that in this case won't (=will not) is a form of the modal verb will. If I get the meaning of won't right, it's the same like in the following example sentence from the Cambridge Advanced Learner's Dictionary:

3. The car won't start.

But I wonder why not simply to say:

4. George runs as fast as he can but the kite doesn't fly.


5. Peppa runs as fast as she can but the kite doesn't fly.


6. The car doesn't start.


7. The car isn't starting.

Are the latter sentences wrong in English? Or do they sound weird?

Answer

All of the example sentences are grammatically correct, and have similar meanings.

There are some differences between "won't" and "doesn't" in this context:

• "Won't" is active, whereas "doesn't" is passive.


• This implies that the subject that "won't" do something had a choice about whether to do it.


• Thus, "won't" tends to anthropomorphize its subject, whereas "doesn't" implies that its subject does not make choices.



• Another way of looking at this active vs. passive difference is that "won't" implies that perhaps the kite could fly, if something were done differently at the time. Whereas "doesn't" implies that the kite can't fly; perhaps it is broken or weighs too much.