You might notice it if you were to stop drinking coffee for a week - slight caffeine withdrawal. Also, I think that a small percentage of the obsession does come from caffeine addiction, the anticipation of the “hit”, etc. “No noticeable effect” can also mean that you just feel normal with it, but a bit uncomfortable (or tired) without.

I wouldn’t underestimate the drug, not anymore - doing a detox made me realize how it’s still a drug that does stuff to your brain and possibly your body.

Of course, YMMV.