In the past, there was a subclass of triggers (“No Visual Effect”) that did not require announcing because they didn’t have an impact on the visual state of the board or require choices. Think Goldnight Commander or Kruin Striker. However, with the simplifying of the trigger rules, those now have to be announced.

Simplified Trigger Rules: You cannot “forget” your triggers. Your opponent is not required to remind you. If your opponent misses a trigger and you want it to happen, call a judge (and you’ll get to make happen if it’s still within a turn). If you miss your trigger unintentionally and the opponent doesn’t want it to happen, it won’t happen.