Social media companies almost never advertise. Seriously, when was the last time you saw an ad on television for Facebook? I guess the idea is that Facebook ads are Facebook ads. Doesn't make a whole lot of sense to me, but what do I know?
Since companies like Facebook and Instagram don't have an ad campaign they have never needed to create a slogan for themselves. However, earlier this week users on another social media platform, Twitter, took it upon themselves to make ads for these companies and you know what? I now see why companies did not have their own slogan before.