Have you written and submitted a vignette? No, don't play innocent. I see you there, whistling and pretending you didn't hear the question.
Vignettes are often some of the nicest writing, and while I realize you don't mean them to be, they're a dirty trick to play on editors.
Deep in the fens of slush, as we beat at the underbrush of bad punctuation and step gingerly (ew!) around the festering piles of crap, not so infrequently we catch sight of something. Wait, is it...! Something publishable? Something sleek and lovely and well-groomed? Yes! It's... No. It's a vignette.
This is like looking for the literary equivalent of an downy white swan or noble 10-prong buck, and finding a fricking plastic flamingo instead. In the realms of getting- the- rug- pulled- out- from- under- you, you can almost hear the "Yoink!"
Lookit. I don't care how charming and beautiful your two scenes / beloved memory / bonding moment is, it is not a story. Nothing happens. No, I take that back. (Jimmy and his dad caught a fish!) Nothing happens that anyone but you gives a shit about. There's no conflict.
These are also sometimes called "mood pieces", and their aim is to convey a single emotion or atmosphere. Yes, ok, Goodnight Moon has no conflict. But I'm not talking about bedtime books.
If some of your favorite picture books are No David, Where the Wild Things Are, and Don't Let the Pigeon Drive the Bus, consider that those books are practically conflict from one end to the other. People love conflict! Think about it. You're reading this blog, aren't you?