They wouldn't pay it unless it made good business sense. And besides "just works" Apple wouldn't want to have to offer a subpar default search offering to their users. So it's always win-win.
I've actually switched, after a long time, to using Apple Maps as my default mapping application. It's good enough for 99.9% of the time. And I like its privacy-conscious construction.
I drive a lot of car KM's in Europe. Apple Maps is bad when it comes to guiding me over the best (read: moving traffic) roads compared to Google Maps.
As much as I enjoy particular instructions (specifically the indication of highway splits) from Apple Maps, Google Maps just keeps me moving and prevents stalls way better over here.
Short distances it matters less. That might be your 99.9%?
I suspect it's that they don't want to take the risk that not being front and center on Apple platforms could have on their business. Maybe droves Apple of users would jump ship to Bing... Or maybe they would jump ship to Android if Google Maps and Waze were pulled from the App Store.
