Ninja also hasn't been around for as long as the other classes. I'm sure there are some out there who simply haven't the faintest clue what they're doing.

If you're looking for a way to help these ninja out though, I recommend the carrot instead of the stick. Point out to them that keeping huton up improves their performance (once you get used to having it up all the time, not having it up suddenly makes you feel like garbage). Some of them probably also don't realize that trick attack is stronger than sneak attack due to its affect on the rest of the party... at a glance, it looks like it's weaker.

Point out that doton on a single target is a waste of a perfectly good raiton.

But just getting exasperated and threatening to kick people until morale improves isn't going to help anything.