Because it's quicker. You trade the mental effort of remembering to dose down over a longer period against physical discomfort for a day or so.

Personally I don't find cold turkey too bad. The second day after I stop I'll have a headachey, nauseous afternoon (which is almost entirely handled with paracetamol as long as I stay hydrated), but after that it's more a matter of habit.

I may not be the best example because i try to quit every now and then... But i feel rthat quitting in steps does absolutely nothing. I would keep reducing and not noting any change in body behavior. Until i go past some threshold (2 espressos) them i get the same as fully quitting

For me at least, I'm at one cup, but still get withdrawal symptoms if I don't have it. Is there any way to meter this down? Maybe just dump out half the cup?

As an opiate addict in recovery, and having experienced caffeine withdrawal: taper, taper, taper. There is no excuse not to.

Going cold turkey is an ego-motivated action, in my opinion. It's the 'If I can endure this acute suffering and beat it, then I'm stronger for it' attitude, and gives a false sense of inflated accomplishment. The reality is that you put yourself through needless torment so you could feel better about yourself, while a rational person whose goal is to actually beat the addiction realizes that their chance of returning to the substance increases substantially with how bad the withdrawal symptoms are.

If you want to quit, do everything you can so that you don't go back to ingesting the substance in question. That means reducing the chances you'll relapse because withdrawal fucking sucks and the only thing that will fix it is either waiting or using again. Guess which one your brain will try to convince you to do (hint: its the one with the least amount of immediate suffering)?