I recently finished a book that was very well written and could have rated 4 or 5 stars if not for the fact that the story hinged on the stupid decisions made by the main character. The character made one major bad decision early on in the book, and I kept waiting for her to fix it, but whenever an opportunity came up, she decided not to and just made things worse. In the end, her decisions damaged her life and the lives of those who love her. What was the point? Why did the author write a character like that? My opinion is that her decisions are what drove the plot, and without those decisions, there wouldn't be much of a plot.
As an author, I've read that a good story is one where you put your characters in extraordinary situations and see how they respond. A good example of this is The Hunger Games. Katniss Everdeen started out as just another citizen of Panem, but she winds up being heroic because of the Hunger Games. Her decisions in the face of her circumstances make sense, from the beginning (*spoiler alert*) when she sacrifices herself for Prim to enter the Games until the end when she threatens to defy the Capitol. The way that the author created a believable but admirable character is one reason why I love The Hunger Games so much.
On the other hand, some writers try to tell a story by putting their characters in situations and having them behave in inexplicable ways. Consider horror movies where a victim who knows about the potential dangers of his/her surroundings decides to wander off alone in the dark anyway so that the killer/monster can butcher him/her. If they were smart and stayed away from the haunted house, dark alley, or creepy campsite in the first place, then we wouldn't have a story, but at least the characters' actions would make sense. Instead, we don't sympathize with their fate.
Maybe some readers enjoy it when characters make stupid decisions, but I don't. I want to read about characters who are praiseworthy. I want to root for them, like I did for Katniss, not hope that they get killed by the bad guy in the end.