Small things can matter a lot.
Staying at a hotel (courteously unnamed here) this weekend, I noticed the push-button console for the elevator in the lobby was askew, slightly off-kilter. In a bathroom off the lobby, a faucet was installed not-quite-parallel to the line of the sink (its top rim). An amber light attached to a hair dryer flickered in the dark of night. The television set in our room had a mysterious wire with what looked like a computer chip dangling from its front, more obviously than a dangling participle.
None of these matters proved fatal, not even severely anxiety-producing.
But they were unsettling to the careful (or even almost-careless) observer.
And the same applies to language.
A few mistakes here and there, a few verbal tics, and the reader gets nervous, distrustful.
As an editor, I frequently tell clients that readers start to distrust your data if you make some seemingly trivial blunders. The readers start to think, "They got that wrong; what else is wrong?"
An example: I received an impassioned plea for church stewardship pledges with "alter" [initial cap] instead of "altar" at the heart of the request. The writer's sacrifice of accuracy was like Abraham's near-sacrifice of his son Isaac. Not quite, you rightly say. After all, there's an infinite gap between sacrifice and near-sacrifice. (And didn't Mark Twain say the difference between the right word and the wrong word is like the difference between "lightning" and "lightning bug"?)
Of course, many don't care about such minutiae.
But, to paraphrase Grace Slick's refrain in the 1960's, "Go ask Isaac."