In various cases it's beneficial to know if triggers depend on a particular trigger and what they are. While you can see what a trigger depends on, you can't get that opposite view. This need first came to my mind when writing http://blog.zabbix.com/a-workaround-for-trigger-based-maintenance/1527/.
Not only that you could explore the chains of dependencies, the implementation should also give you an idea about the consequences of deleting a trigger that others depend on. The behaviour is also slightly inconsistent, if you compare with what I reported on
Action conditions: When you delete an entity referenced in a condition, the reference is removed and the action is silently disabled
Trigger dependency: When you delete a trigger that other triggers depend on, the reference is removed, but the trigger remains enabled