Coke had their reputation and near pornographic delicious propoganda ads in movie theaters. That makes it easy for any person just living life to buy a coke over something else.

It's actually super easy most people to switch to another brand or try something new ("sorry, we only sell Pepsi products" means you've tried more than just Coke). It's always been easy but they had people mentally on the hook, that wasn't too easy to snap out of for most people and Coke is losing a very good thing they had going for them.