the service will be a good way to play Playstation games for people who only are interested in a few story-single player games (competitive multiplayer games and very latency depended games like Beat'emUps will be significantly better to play on the real console for atleast the next 10 years) to get their fix without having to pay for a console
Sony is trying to increase their userbase that way, which looks very essential for the industry as especially highly cinematic games are becoming more and more expensive to produce
with PSNow a publisher that releases on PS systems also has the option to serve their games to hundreds of millions of smart TV/ smart device owners with no additional effort