Most psn games require online activation in order to use it otherwise, it will tell you to sign in on the store to renew it. That's been defeated with reactpsn.
Forcing the user to stay online is not the smartest thing. Your ISP goes down for a few hours, or you chose to go to another isp but you wont have net for a few days, or simply, or your wifi router stops working and in the mean time you're too busy to go get another one and you just want to play for a couple of minutes.
Restricting you to online-only is a very risky thing, in some places the internet isn't a luxury, some can't afford high speed internet.
Smartphones are not online 24/7 , I can choose to disable wifi and turn off data and I can still use the things I've purchased. Unless they put a sim card on the ps4.
Piracy can't be stopped, you can delay it, but never eliminate it.