I thought at first people were spiking their tea. I couldn't figure any other reason for its pervasiveness. The first few days I was in Buenos Aires I noticed it everywhere. People with thermoses in their cars. Groups of 11 year olds in parks. Old dudes sitting at cafés and bus stops. People even had designer leather carrying cases for the equipment.
Mate is a traditional South American drink brewed from the yerba mate leaf. It is prepared in a gourd which is filled to the brim with the ground leaf.

Hot water is poured in and you drink it from a bombilla a type of spoon/straw which filters out the leaf from the bottom. Custom dictates that only one person be in charge of the water. He or she (cebador/cebadora) fills and passes, fills and passes, fills and passes.
Mate is not just a drink it is a social and cultural event. No one drinks mate alone. It is for the group. It is for sharing. The idea of mate sin people is a foreign concept. The enjoyment factor is born from the companionship. There is nothing quite like it in the states. The first thing that came to mind is a smoke circle, but even that is a social event leached from other cultures. And besides, the event of mate can last hours without mind-altering effects.
Mate transcends class, religious, and ethnic differences where are pronounced manifestations in South American societies. There are borders everywhere and between everything and yet when mate is filled and packed everyone around is invited and welcome to the circle.
There is a companionship to it and a tradition dating back centuries. People have done it forever, before neo-liberalism and before European colonialism and it still persists. Hell, not only does it persist it thrives. It's everywhere you look. And where there is a mouth to a bombilla there is also companionship and friendship and equality at all parts of the circle. Modernity does not spite mate as it does other cultural traditions.
Mate is drunk in public. Privately as well, but also shamelessly in public. What happens to a culture who performs such an event for all to see? Does culture have to be public to be culture?