Your argument can also be used in a similar fashion to say that if I wait a year and two and not buy a game day one, then I'll be rewarded for my patience by being able to buy the game for 50-75% reduced price. If everyone followed that same train of thought, there would be no day one sales because why would you pay double or triple the price when you can just wait a while?
The point of PS+ is that by giving away a plethora of games at low cost, there is a chance that one of these older games will become your new personal favourite for which you'll buy DLC or the sequel. Personally, I would have never bought a game like Soul Sacrifice, but because PS+ gave it away, I now am hooked and will buy whatever sequel comes out day one, expanding the market for an otherwise unappreciated game.
