We don't really care about tournaments at all. We do take students to them from time to time. Because they want to go. But it's not at all a focus of the way we train.
Difficulties do arise, most commonly because we don't limit ourselves to WT-style tournies. And open tournies have widely varying rule sets. A couple examples.
We took a handful of students to an open tourney. I competed in the weapons sparring, using shinai. Their rules did not allow strikes to the head.
At another event, we were told that you would not score if you pulled your strikes. Hogu, headgear, hands and feet. One of the students I took was 13-14. She was a blue belt, so she'd been training with us a few years at that time. She was told the rule was contact, but I also specifically told her not to go 100% power. One sidekick to the abdomen and her opponent declined to finish the match. It wasn't a full power shot by any means, but apparently their definition of contact and ours differ.
And, frankly, reflexes can be a problem. At one of the few WT-style tournies we've been to, I had a 1st Geup student DQ'd. Because he simply couldn't stop punching people in their wide-open heads.
Those issues could all be resolved by spending time training under the rules in force. We do not. If students want to go compete, we discuss the rules as published for that event, but we don't spend any significant amount of time training with them.