[flukus]

They're non-obvious and can bite you in several ways. A lot has been written about why triggers are bad (random example: https://www.itprotoday.com/development-techniques-and-manage...). Back before service layers were common and desktop clients connected to the database directly they were common and just about everyone has some war stories of triggers breaking things.

[cryptonector]

A lot of things are non-obvious, especially when you're not aware of them and don't expect them.