If you have demonstrated the ability to quit any time you want, is it an addiction? Or a tool you find useful?

The technical term is "dependency". Caffeine causes physiological changes, and withdrawal is unpleasant.

I've tapered caffeine successfully by measuring out instant coffee. This works pretty well for managing the physical effects of caffeine withdrawal, or at least spreading them out. Basically, I 1) committed to only having the same exact amount of instant coffee, at the same exact times, every day, and then 2) every so often, reduced it a bit. Then I switched to a very moderate amount of decaf (which, yes, has a little bit of caffeine in it, but not enough to cause me problems).

I did this because I was getting withdrawal headaches most mornings, which is an unpleasant way to begin the day- I wasn't even drinking that much caffeine!

Caffeine doesn't have a strong psychological addiction, but it's physiological withdrawal symptoms are bad.

I have not found a drink equivalent to a coffee to drink in the morning. This is my psychologic addition.

All these fake coffees (I’m looking at you, chicory root) taste like ash-trays from the grimiest bar in town.

Ginger shots made at home with some orange juice or apple juice help a lot.

Maybe for you it doesn't have strong psychological addiction, but for me it certainly did.

I never really liked coffee, but I drank it at work just as a pretext to talk to other people.

I didn't have a coffee maker at home at that time. So I started getting headaches on Sunday. I made the connection eventually, after my headache completely disappeared 20 minutes after drinking a cup of coffee with a friend.

This appears to be a pretty common scenario.