Unless you have had extensive practical experience of actually dealing with real people who attempted to replace soda with water and with real people who attempted to replace soda with juices, I have to doubt your opinion on what's "practicable" and what's not.
Oh, and everyone with a crappy diet gets told to improve it. Guess how often that actually works?
P/S/A: There are single sentences which can create life-changing amounts of difference.