One of the things I love about urban sketching is it's social. When I paint in my studio, it's a solitary experience. But sketching in public invites people to ask what you're doing and watch and make friends.
On my recent trip to Seattle I sketched people celebrating a birthday by dressing up and playing Clue on the train.
Met a group of amazing people from Wisconsin attending a convention for teachers of kids with special needs
And met a fellow sketcher for coffee every morning and doodled, told stories and exchanged drawings.
My trip was so much richer because of the people I got to meet through urban sketching. Visiting a place is a 2-dimensional experience unless you include the people that live there. I love that urban sketching makes that so easy.