Its not a comment on the importance of Twitter. But rather composing a tweet requires no considerable effort. Its the same as when people change their FB profile pic and considerate it action.

An action that involved real effort would have been a twee that contained a link to the AirBnB's program to help alleviate the problems faced by refugees.

The President of the US is an odd example because that runs counter to your point I believe. Trump Tweets are the ultimate symbol of vacuousness, vanity and impulse.