The obvious reason to scorn Yahtzee is because it's a successful mass market game. The gamer subculture can certainly have some elitist tendencies, although I swear that is dwindling as destined games become more mainstream.
However, Yahtzee also is luck-dependent, involves no interaction with the other players and has zero theme. Any one of those things can be a turn-off for some folks and they are all legitimate gripes.
Despite that, I have come to enjoy Yahtzee and have lost any scorn I might have had for it. It's an easy game to cobble together and teach. More than that, it does help teach odds and dice evaluation. It isn't as random as it looks at first.
I even went through a spell of regularly playing Yahtzee online. If I woke up early and wanted to get in a life game without getting out of bed, Yahtzee was a game I knew I could find an opponent and finish a game before I had to get up.
Still, Yahtzee is never going to break into my top 100 games. It's not a game I would actively seek out or suggest to play. Yeah, if someone really wanted to play, I would play Yahtzee and I would have a decent time. However, what I have come to truly love about Yahtzee is how it has been a stepping off point for so many other games.
Simply put, getting two re-rolls and trying for specific combinations of dice faces is a fundamental mechanic for game design. It is one of those bed rock concepts.
I know that Yahtzee didn't invent those mechanics from scratch. Dice games have been around for thousands of years. But Yahtzee helped codify the formula and helped spread it around, particularly for the non-gambling audience.
There are literally hundreds of games that are built off of the Yahtzee mechanic. I am not even going to pretend to try and list them all. While some are frankly garbage, others are genuinely good.
And the ones that are fun address the issues that I brought up before. Games like To Court the King add special powers that five players a measure of control. King of Tokyo not only adds interaction by having folks beat each other up, it embraces the rich theme of giant monsters. And that's not even the tip of the iceberg.
Yahtzee has given us a way of understanding and using dice that has created a lot of fun experiences.