It's a bit of ambiguity of grammar.

"X don't Y" generally means "X never Y" (ex: "Grapes Don't Grow On Trees").

However, adding Why to the front of X Don't Y ("Why X Don't Y") does not necessarily mean "X Don't Y. Why?" - rather, sometimes it's actually asking "In cases when X do not Y, why not?"

In other words, you can't necessarily parse the sentence by simply parsing "X Don't Y" by itself and then applying "Why" as a question to that. That was what I was trying to illustrate.