I live in Greece, and it is an optional extra here. If you pay with a card, a lot of times there is a menu on the POS which you choose a percentage for tipping, which ranges from 0% upto I dont remember how much (but a lot).

Personally I always give a generous tip, (unless the server intentionally does something bad), just because it feels good to. It is not charity or pity for low wage. It is just that I would welcome a tip too if I were in the waiter's shoes, no matter how much my wage would be.