There are people, who judge a game's worth based on how much content it has. They are trying to get as many hours of gameplay as possible for the money they spend. But that is really not a good way of selecting a game, because if the game is bad, making it longer only makes the experience worse. Even if you are truly broke, there is so many freeware and free to play games, that you can invest the little money you have into hardware and just play those.
A really good game can be very short and still be worth a lot of money. And there is almost no limit to how short a game could be. Multiplayer games are a great example. An average match is like a half hour at most, so you are playing the same half hour game over and over again.
Often, when a game is long, it is because it has a lot of padding. Parts, where no new mechanic or challenge is presented and you are just doing the same things you did before. Some people like the feeling of familiarity, but they would also get that by playing a short game second time. And while I could quit the game at any time, it does not seem right when the game has an ending.
Of course, that does not mean that games should never be long. Some games are designed in such a way, that their quality would suffer, if made shorter. To keep the quality high, developers should simply avoid adding content only for the sake of increasing playtime and players should not assign value to how long the game is.