Sony is disappointed in Mobile because it is loosing them Billions. Along with the drop to 9 Million units sold they are also forecasting $300 Million in losses.
That would not be the case with 5, 10, or 15 Million PlayStation Mobile devices a year.
If done right the investment is in a scalable ecosystem, so everything they do benefits every product. No more Mobile Communications VS Home Entertianment and Sound VS Game and Network Services VS Pictures VS Music, with each team building their own products to compete against each other. Instead, Sony would have one OS team, one App team, and one Network Services team. Everyone working towards a common goal and cutting out redundancy.
This puts more people on their OS and Store Front more of the time, with no fragmentation, which means more revenue and profits. The PlayStation 4 OS and Store are the most profitable thing at Sony, adding more ways to access the OS, Apps, Games, and Store will only increase their Revenue and Profits.
PS4 started at zero 5 years ago, and it is now profiting in the billions. Switch has been out almost a year and a half, and it has been a very successful device so far. Yet neither one runs, Android, iOS, Windows, or MAC OS. You don't need Android, iOS, Windows, or MAC OS to make a successful and profitable device.
What makes you think they would even sell 5 million? Why would they make a playstation phone with added performance and and better quality, more complex hardware for less than they're charging for their current phone lineup? What makes you think if they're losing 300 million selling 9 million phones when they don't even have to support the OS and build up app support that it would be more profitable to do that, only sell another 5 million phones, and not be in an even bigger hole?
So you want to put the Sony music record label types... making an operating system and applications. Same with with their movie making company? Do you know the first thing about those industries? i can assure you, the apps they make for their services are just a drop in the bucket. The fact that they need to make apps for windows, PS4 OS, and android is not the issue even a little bit. At this point, I have to ask, do you know the first thing about software development? Never mind that even if Sony were to make a playstation OS for their phones, they would STILL have to make iOS and Android and Macand Windows versions of their applications and network services because you cannot expect your install base to automatically switch to your operating system. Why do you think Microsoft makes Office for Macs? Do you think they do that out of the kindness of their hearts? Our of a sense of fair competition? No. It's because they want to firmly establish Office as "the standard" and that means making sure everyone can use it. They'll still have to do everything they're doing now *and* support a new OS in ways they've never done before. Again, how is this going to make them more money?
They have already added more ways to access apps games and store. Playstation Now says "Hello!". It just makes zero sense to make an entirely new OS when an app will be nearly as effective without forcing a user to decide between Playstation and everything else. This walled garden approach you want Sony to take hasn't worked for Microsoft every single time they've tried it. Yet you still think it's effective because Apple got it right, and Steam kinda did too, while ignoring the dozens and dozens of failures. People just want to use their devices in the most convenient way possible, not in the way that's most profitable for the companies they support. It won't be more convenient for an Android user to switch to Playstation OS, not now, and almost definitely not ever.
And by the way, PS4 did not start at zero 5 years ago, it had the momentum of over 15 years of the Playstation brand pushing it right from the start. You're grossly, grossly oversimplifying things.