Originally Posted by SFOSpiff

Basically personal calling cards. Very popular (even socially required) in Victorian times. Sooner or later everything comes back in fashion.

It is amusing, though, that as we've reached unprecedented levels of electronic automation that we'd introduce new paper-based methods of contact... kinda like how America spend a century paving 4M miles of roads and now people want SUVs so they can drive on dirt. Humans are weird.