Books and websites on writing tell you to cut, cut, cut. They tell you to ask yourself if each scene, each paragraph is necessary. Advice on writing for children warns against brick-sized manuscripts in tones implying that most writers are dying to indulge in thousands of words' worth of backstory and description. My sense from the above and from various conversations (most recently at a Kidlit Drink Night) is that it's a fairly common tendency, though the observation is obviously anecdotal.
I've never had this particular problem, and I have to admit, I find it a hard one to understand. Maybe it's because I've spent more time reading children's and YA books than adult books. Maybe its roots run deeper: my childhood difficulty with the motor skills involved in writing meant that my school compositions were short, sometimes too short. It's not that I've never written an extraneous sentence or started to explain something to the reader before I realized it was already obvious. But "writing too much" as a vice? That's a vice that takes a lot of work and a dedication that I can't help admiring, even as I value tight writing and showing over telling. Maybe, though, it's easier for some writers to get all their ideas out before they start chiseling; approaching writing that way could make it less intimidating. I imagine genre makes a difference, too. Fantasies, particularly those with extensive world-building, tend to be longer than realistic stories, and writers who are inclined to create whole worlds might also be inclined to spend a lot of words doing so.
Other writers (of fiction, nonfiction, or anything in between), I'm curious: Do you find it's easier to write too much or too little?