That said, I would never work as early as 9am if I didn't have to. Caffeine allows me to jumpstart my brain for programming. I need coffee in particular: tea sustains but doesn't jumpstart.
Exercise first thing in the morning can act as a substitute for coffee in getting my brain jumpstarted. While I find it easy to exercise at 6:30-7am in the Summer and Fall, Winter and Spring in southern New England suck. At 6:30am, it's often dark, 10-20F, windy, and damp. It's an area made for depressions. I can't see ever giving up coffee while I live here.
It's important to point out that about every decade you're going to have to adapt your diet and exercise to meet changes in your body. I'm 53 now. When I don't exercise at least 5x/week I start to have sleeping issues. Alcohol affects me more, especially my sleep. Carb bombing happens with a portion of half the amount I could eat 10 years ago. Back to coffee, I have 2 espressos in the morning and, occasionally, one after lunch but never after 2pm. Breaking any of those coffee "rules" causes me hypertension, sleep loss, and/or a sour stomach.
Sorry for the tome. Hopefully some of it is useful.
However, people have wide variations in what they taste (and smell) as pleasurable. Without reading the study, I have a hard time being as binary as "nobody likes the taste of coffee".
In reality I have quit caffeine and gone back to it. I didn't see the same benefits as you. After a few days of adjusting, I felt about the same as before. The only difference was I didn't get to enjoy a morning coffee anymore.
† It probably wasn't really by Mark Twain.
It really helped along with not drinking all the gunk in soda. Since then, I've cut salt intake, sugar binging, and set aside 30 minutes most days to get the heart rate up. I'm no "health nut" but after breaking my sedentary habits, I do feel better than I have in a long time.
What happened for me was winter. I was waking up at 7, running every day in the morning, working on a project before work. Then winter hit and seasonal depression makes it hard.
So now I'm waking up earlier, and doing more work, but I'm using coffee again....
Unfortunately for me, this is a feature.
Even when I go a week to a month without caffeine, I tend to stay up late, but not late enough to get things done.
However, if I drink something caffeinated, then I can turn that into staying up late enough to work while it's quiet, and I become much more productive.
There are other reasons as well, however they are more specific to my personal scenario, and not really generally applicable. If you're curious, I'd be happy to talk about them in some other way, but not in a public forum. (My email is in my bio if anyone's interested.)
The body is too effective at regulating anything that feels good.
We'll see if the trick is to eat healthy and exercise instead of doing neither and then acting like it's the coffee that's going to kill you.