Partly the tourist thing and partly the size of the shop. Definitely in places like convenience stores and small restaurants that are usually only frequented by locals, you'll have a harder time using a card without a chip, or sometimes even ANY card. I've had this happen in London, Prague, and Zurich, mainly because I like exploring local joints.

If you do stick to tourist zones, you're probably ok. Agree on ticket machines. Had that experience in Paris and Zurich where it wouldn't take my chipless card.