Genuine question here, not having a go, but do people feel this way because they want to play many games and want to feel up to date?
I myself, due to limited money, love games that give you lots of content for your money. I will play games like witcher, divinity, and yakuza games for months. I've been playing TW3 for a third time, since January. That's not to say I don't like smaller experiences too. I feel that when it comes to shorter games, my standards aren't necessarily higher, but different.
I've also seen this view in the review and coverage industry, which seems like a need for those people to stay up to date, or give appraisals fast. I try to consider this when taking into account their opinions actually, especially because I'm someone that likes to walk and smell the roses.
I guess it could also be that people want to experience a variety or simply just get tired of things. I definitely think I'm quite patient when it comes to long games too, I will give a game I know has depth or length to it a lot more hours than a game I know is a shorter experience, though I'd probably just end up playing all of a short game anyway.