Well, caffeine is addictive, and many sodas have caffeine in them, so it is not a 'used to it' thing, it's very physical[0]. When you order that diet coke with lunch everyday, you develop a habit that is very hard to break for a lot of folk. Also, enjoying a Dr. Pepper is not terrible, you just have to know you are drinking a lot of sugars.
As an aside, the sugar profile of most sodas is made to mimic that of honey closely. So much so, that 'stretching' honey is a cause for concern in apiarist communities as it is quite easy to do so [1].
As an aside, the sugar profile of most sodas is made to mimic that of honey closely. So much so, that 'stretching' honey is a cause for concern in apiarist communities as it is quite easy to do so [1].
[0]http://www.caffeineinformer.com/caffeine-withdrawal-symptoms...
[1]https://www.ncbi.nlm.nih.gov/pubmed/23575142