Decaf can be harmful. Depends on how it is made. There's also a difference in taste, at least I feel. One can get "addicted" to anything. If someone starts eating a lot of salt, he gets used to that amount and then everything seems saltless. With sugar it is the same. I used to drink my coffee with sugar, but for many years I drank it without. In the beginning it tasted very bitter, and now if I drink it with sugar it seems too sweet. It's all a matter of habit. If someone thinks coffee is harmful, he can never drink. Those who want to can stop drinking tea, because they can get "addicted" to it too. If you drink tea every day, you get used to it and you want to drink it. Whoever wants can live without any "stimulants" and drink only water.