Copyright infringement is the official descriptor but that doesn't mean "dude you stole dat game" isn't a perfectly reasonable statement to make in a non-official capacity. You can't steal a woman because they are not possessions (dammit) but people certainly say "you stole my girlfriend you bastard."

The problem with it as you well know is that the vast majority of humans are selfish dipshits who, when given the option to decide if they want to pay or not, will not part with money easily.

And even you, who I do believe is more honorable than most, have made comments like "hey I finished this game and liked it but I am waiting for it to hit $20 to buy it" and shit like that.

The only way I could see try before you buy working is if you put strict limits on yourself to the effect of limiting the time you can "try" something to like 2 hours and only playing more once you buy the game.