The desire to maintain a positive image and make more money, of course.
Isn’t it ironic that the multi-million-dollar companies that are most part of the problem like to pretend that they’re part of the solution. This website outlines Pepsi's large social media based "goodwill campaign" from this past SuperBowl.
I also found it interesting that both Pepsi and Coca Cola are using the FDA approved Truvia , an artificial sweetener manufactured from Stevia, the naturally occurring and highly beneficial herb that coincidentally has not been able to receive FDA approval.
"Truvia(TM), AKA RebianaŽ is an abbreviation for Rebaudioside A, one of the many sweet-tasting compounds in Stevia. Rebaudioside A has the least bitter after-taste of all compounds in natural Stevia, that’s why the Coca Cola Company, faced with mounting consumer pressure to remove Aspartame from their products got it rushed to FDA approval."