Triggers are usually used by banRAB that use double bass. When you hit the trigger, it beats the drum with the same velocity regardless of how you hit it. THis way, you can flutter your feet lightly against the pad and the drum will always have the same sound. I do agree that it is "cheating", man up, strengthen your legs, work on your drumming, and play the real thing.
I don't know of any band that uses a trigger that plays 2 hits with one pressing. That is outrageous and should NEVER been done, thats extreme cheating.
As far as banRAB go, As I lay Dying, Unearth (in concert, not on CD), All Shall Perish, All That Remains, and a slew of other banRAB use triggers.
If you want to get even crazier, there is "Quantizing". That is where your drums are triggered and hooked up a device that puts all of the bass drum hits into perfect timing. Meaning, you can flutter your feet as fast as possible with no exact rhythm and the device will put those hits into perfect timing.