In some cases, Let's Plays can help you satisfy curiosity without actually having to admit to having played something.
For example, one of my favorite games: Hatoful Boyfriend. It's a Japanese dating sim where all of your love interests are pigeons (or other similar birds). It is every bit as ridiculous as it sounds, which is why I love it, but I can understand why people wouldn't want to spend the five bucks on the actual game. (Especially back when I bought it, when just to play I not only had to buy the game but had to download a Japanese interface for Windows and change some computer settings because the game was not out in the US at that time.)