The value is in owning the customer relationship in most cases for the major players.
The capital scale of these solutions has gotten very to extremely high. That reduces incentives to compete in these spaces.
Apple doesn't particularly care to run a search platform because they can extract much of the value of search in allowing others to serve that market (ie, microsoft or google). Ie, these become high profit plays while letting someone else do hard lifting. I'd expect however they would fight like hell if you tried to take away their relationship with their customer.
Even in places they compete - not 100% sure it's worth it. They are fighting it out in maps at huge expense. You need to deliver a global map to your traveling customer base that is amazing (transit, traffic, local POI etc). This is not a small project. Then you have to monetize it. If you told me a smaller handset provider was going to launch a mapping solution - I'd tell you they are crazy!
That drives cooperation especially if a solution is a high capital requirement. Even intel is probably going to cooperate with TSMC (!!!). Some of these capital efforts are kind of insane - 30 billion per year capex type stuff. How many countries have CAPEX expenditures in this scale (ie, not just on operating costs / staff salaries?). These business are larger than countries in some cases.
Android / Samsung absolutely are competing (and copying) Apple in handset space. Ironically they will first denounce apple (not shipping chargers!). That's ALMOST always a guarantee that they will then copy them next cycle :)! I'm not kidding. I'd love to go back and look at everything from an all screen design (bad email machine), to dropping 3.5m jack (which I hated to see happen) to dropping chargers etc.