That's fair enough. But Sony is not going to leave more income on the table by excluding the PC market. They are including the PC more and more.Timed exclusives from third party is different story. From first party only one game has been ported.
Selling hardware at a loss while gaining back the cost with games and services means a shorter return on investment with a larger market. That means that if you can easily port the games to PC, it's worth the investment, especially because the PC doesn't really directly compete with the consoles.