I can't explain it, something about the freedom of acquisition takes the pressure off and lets me just launch it and try it out.
Maybe it's easier to pay some money and hit "install", than it is to find a torrent, download it and go through the install process, so there's a selection bias there.
Maybe it's the fact I downloaded it exactly when I decided to and not when a sale happened or it was in a bundle.
But even then, when I decide I want something right now and I pay full-price, something about that just puts a psychological barrier in between me and enjoying the game. Like now I have to validate the purchase, and if I want a refund it has to happen within 2 weeks, and within 2 hours of play (for steam). It's just an unpleasant feeling.
Even worse is the subscription model. I absolutely hate the pressure of having to try all the games I put on my list before the end of the month so I don't have to renew to keep trying them, that just feels like wasted money. But then about a week into the month I'll lose my energy for trying new games and I'll let the sub lapse and never try a bunch of the games I wanted to. It's the worst way to pay for games, even if on paper it's the cheapest for trying a bunch of them legally.
Very occasionally a game will come along that I know I want and will happily pay for immediately, and usually that means I'll give it a decent try.
The best experience for me is pirating a game and loving it so much I then buy it, that guarantees I'm going to play it a lot. The latest game that happened to me with was A Dance of Fire and Ice. I bought it like 5 times, once each for me and my two kids, and twice on phone, and I was completely happy to. I even built a custom rhythm controller for it.
Funny story though - the pirated version of ADOFAI puts savegames in user folders, but the steam version puts them in the game folder, so it merges the progress between users. So for that reason, the pirated version is better. I can't explain the discrepancy.
I guess I'm talking about launching and trying the game, rather than finishing it. Like once I start playing, the chances I continue are mostly about the game itself, and probably more about my mood at the time than I'd like to admit. I'm talking about games languishing completely untouched. As someone that's been collecting a steam library for 20 years, I've got well over 1000 games and I haven't played even close to half of them. I play almost all of the games I pirate. I've only started doing that a lot in the last year or two, but even in that time I've bought a bunch of stuff I don't play. The pirated ones just call to me stronger.
I think it's just you.
I wouldn't buy a game if I'm not going to play it though.