Coming from the UK, added service charges always annoy me (unless it's for large parties). A tip is something that I volunteer to express gratitude for a good experience. It is also something I can refuse if the experience is bad. Forcing a service charge assumes I will pay X% more than the price I have been shown regardless of experience.
However, that view is based on the UK system where minimum wage for the serving staff is enforced and where tip pools are allowed.