There is a fundamental difference between text and live video. If someone texted you that they they are Obama and they want to be friends, very few people would believe it, some may still fall for it no doubt. But now someone video calls you and you see Obama on the other end, and you’re able to have a conversation with them, then a lot more people would believe them.
Chat rooms were inveted shortly after the invention of the internet. People lying about their age on the internet isn't something fundamentally new.