If I'm trying to explain something while sitting on a terrace, I'm probably talking to the person I'm trying to explain the something to. The only use a pen and paper is going to be is drawing little diagrams to try and make the verbal explanation a little clearer. If I need to write something down to remember for later, I'll just jot it down on the smart phone that I "lug" everywhere with me anyway.
Besides, the prerequisite to explanations on terraces is usually copious amounts of alcohol. Drunk writing is usually as illegible as drunk texting.