Hemingway also hated (or at least avoided) adjectives and adverbs.
Homework: find an Elmore Leonard book, find a few pages at random, and see how many adverbs there are. (I'll do that, too.)
Elmore's style - and Hemingway's - is terse and sparse. Extra adverbs would only slow down the action and change the mood.
But it's too much of a generalization to say that "professional writers discourage adverbs". Writers like Hemingway and Elmore prefer unvarnished prose; other writers use them as needed to amplify what's going on, to tell how the characters moved.
PS: You can find links to the rest of Elmore's tips by searching for that sentence. The rest of what he said (just before it) was "4. Never use an adverb to modify the verb ''said'' .
The extreme case of violating this principle is in the "Tom Swift" books (popular in the early 1900s). Search for "Tom Swifties". Example:
"Who would want to steal modern art?" asked Tom abstractedly.
Almost every "said Tom" was followed by a catchy (but unnecessary) adverb.