I suppose it’s like anything: chances are you won’t have a problem, but that doesn’t mean it’s the right/smart thing to take a chance on.
From what I understand, without a patch, you risk air and moisture getting in between the layers of the tire, possibly leading to tread separation and tire failure. Personally, I’m going to spend the 50 bucks to do it right.
Having said that, I’ve also used the plugs for a temporary fix. Very handy for situations like GBA’s.