Not sure where you have (or haven't been), but I've been to several countries where I've tried to tip, and it's confused or even embarrassed the staff. They insisted I take my change. Granted, this was 15-20 years ago, and unfortunately tipping has become more pervasive, not less, so maybe if I were to revisit those places, things would be different.

But I do know this is still the case in Japan. Some Japanese service workers or small business owners will even be insulted if you try to tip.