Steem, and all the world of crypocurrencies, are revolutionary, created to be exactly the opposite of traditional way to do things. Using "tú" makes it personal and modern.
.. and older people don't want to be called as "Usted", you know it when you are old, or starting to be one.
Well, that's your point of view. And I know it is not only yours - many many many people would agree. Current trend is "tú." I wonder if that would change eventually.
Older people don't want to be called as "Usted" when it's a friend, a family friend, or even an acquaintance. It is certainly shocking when a girl on her 20s says: "Señor, ¿qué hora tiene?" However, it is OK. "Disculpe, ¿qué hora tiene?"
And not only older perople, but even teenagers would be pleased when hearing: "¿A dónde quiere que le lleve?" or "¿Qué gusta ordenar?"