There are getting 15B to NOT boostrap their search engine. If they bootstrap their own engine, they loose 15B on top of having to pay to build this own engine.
Exactly. Plenty of risks involved - they could just fail like Microsoft did, or if they pull it off it could seriously upset the balance in the ecosystem. Better reach a mutually beneficial agreement with everyone's "favorite" search company instead. Coopetition lol
Not worth it. It's not cheap maintaining a search engine. Apple could throw resources at it but what is the benefit? This is different than the Maps issue where Google refuse to provide new features for iPhone Maps. Apple used OpenStreetMaps (OSM) and created their own. By using OSM, it gave that project more visibility and others an alternative solution to Google Maps. A few years later Google suddenly makes it "not so free" for businesses displaying a map, they better put up a credit card.