I'm not sure about other countries but if you notice, there is a trend among Indians when it comes to DP (no, not the one you're guessing!). We tend to put up pictures where we are either sipping something or about to sip. For some reason, it's happening! No, it's not a recent trend. I've been noticing it over half a decade now. Maybe there is a tendency to show that we are enjoying life, either with margarita or cocktail or mocktail or colorfuldrinkwhosenamedeludesyou. It's must be a euphemism for celebrations. Whatever it is, this phenomenon tells you that you were once very thirsty for a memorable picture.
I'm yet to come across a display picture wherein somebody is drinking water.