I am asking because I've never owned one, and have never felt a need for one.

I keep my bike on the large ring (50) for 90% of my riding.

I know "cross chaining" is frowned upon by many, and If I am in a climb long enough, I will shift to my smaller ring.

If it's a short climb, I admit, I cross chain it.

I guess this bad habit comes from my first road bike (over 20 years ago) that would drop the chain if you shifted the crank under load (which is the only time I needed to).

That said, since a double seems way more than adequate for any scenario I have ever encountered, why do triples exist?

Is my lack of knowledge because I ride hills instead of super long inclines?

Is there a terrain where 30+ gears in necessary?