Every fledgling writer hears all sorts of "dos and don'ts", rules that you NEED to follow if you want to have ANY CHANCE of getting published. Most of these things are nonsense, essentially trying to quantify something that is more gut-feeling than hard and fast rule.
Years ago, I was at a conference, where in the opening pages agent-author seminar, the agents stopped reading a participant's opener as soon as they hit an exclamation point, and stressed that shows lazy writing. There must be some other way to show the emphasis, or else don't emphasize the point where it is used.
I have to admit, this one, in particular, strikes me as especially arbitrary. Exclamation points show lazy writing? Incorrect usage of exclamation points can certainly be problematic, but to exclude their usage altogether? Absurd. I'll say again with emphasis: Absurd! (Especially considering one of the events at that conference was titled, "The Power of Positive Writing!” Yes, with the exclamation point.)
But more to the point, there are only three punctuation marks that can end a sentence. Why avoid one-third of them completely? How is that lazy writing? I don't know. It's a fundamental part of punctuation. It would be as if someone said, "I never like seeing quotation marks. There must be some other way to show a character is speaking."
The advice, as a reading rule itself, I find almost obscene. It's a step away from saying, "If I see a sentence with two words that start with a 'k', I stop reading." I shudder to think of fledgling writers running to their manuscripts and slashing out exclamation points. Because THEY! MUST! GO!
I'm so glad neither my agent nor my editor follow such a silly rule.*
*- The first sentence of Thorn of Dentonhill is "Thief!"