I'm not sure why short stories aren't more popular. Sometimes I think that the popularity of a book is a function of how easy it is to talk about that book. Non-fiction (esp. nonfiction about politics, pop-psychology, etc) is very easy to talk about. Novels can be easy too. You can summarize a novel plot-wise, without ever appealing to its themes or emotional content. It's like a movie. Just, The book was about this guy in a situation, and it was good!
But if a novel is like a movie, a short story collection is not like a television series. There isn't an overall plot or set of characters. A collection is made up of discrete elements, which makes them hard to talk about in aggregate. Unless you want to get into the awkward territory of emotional resonance (and don't do that)(Seriously. There is nothing more awkward than people talking IRL about the really individual and vague emotional responses they have to art), you're limited to, Did you like this story? How about this one? Yes, it was very good, wasn't it?
It may also be the (not totally unfair) sense that contemporary short fiction mostly trades in a narrow band of unhappy subjects borrowed from the tradition of Raymond Carver et al.: quietly desperate people having extramarital affairs or caring for sick loved ones or just sitting at kitchen tables becoming alcoholics.
Not all stories are actually like that, of course. Take Jim Shepard's Like You'd Understand, Anyway. Shepard is famous for his careful and thorough research. Most of his stories are historical in one way or another. The first story in this collection is about three brothers at the failure of Chernobyl. Another is about a sentry at Hadrian's Wall. They are stories deeply concerned with context and with jobs or work, and so on their surface miles away from small interpersonal dramas that might seem to typify the medium.
And they do have lots of energy! Each piece has a clear hook, and there's a certain fun in absorbing the context and trivia of each new setting. But the three stories that I think were best were those closest in history and space to here and now. One is about a man who has set up an appointment for a vasectomy without telling his wife. One is about a boy whose younger brother is suffering from mental health problems. One is about a fatherless high school football player. As much fun as it was to read the wilder pieces about Russian Cosmonauts or Nazi Yeti-Hunters (really), it was these three smaller-scale narratives that floored me. Shepard is--for me--at his strongest when he's at his most quotidian.
Because stories are more like poetry. Their value comes from moments, these little shinning diamonds of language and perception that just kind of jump out at you and elevate everyday experience. Or maybe that makes stories more like jokes. They take those secret, half-formed thoughts and experiences you have somewhere in the back of your mind and bring clarity to them in a way that just knocks you on your ass.
The reigning queen of the quotidian is Alice Munro. I had very nice things to say about Runaway, and Hateship, Friendship, Courtship, Loveship, Marriage is similarly great. Her stories are very long, and all kind of meander, but she somehow manages to keep them feeling tight by the end. It may have something to do with the cleanness of her writing on the sentence level, or it may be how well she manipulates time. I'm honestly not sure how she does what she does. But finishing a 40 page Munro story often feels like finishing a short novel.
I've seen Robin Black, whose first collection is the awesomely-named If I Loved You I Would Tell You This, compared to Munro. And at Black's best, I can almost see it. But this collection was much more uneven than anything by Munro. For all Munro's meandering, her stories usually have a mysterious sort of gravity that keeps the elements fitting together cleanly. Black's little observations about everyday life seem sometimes like diversions rather than essential drivers of story. Black's stories are looser, sloppier if I were being a jerk about it.
Still, some of the pieces are very good, and nearly all have at least one moment of real emotional weight. I think about the first story, in which the protagonist--a father whose teen-aged daughter was blinded as a child by an exploding aerosol paint can (and who is having an affair)(of course)--reveals that he had found the boy with whom she had been playing when the accident happened, picked him up and started to shake him as hard as he could. "Shake it harder, Lila. Shake it harder. Is that what you told her? Is it?"