Scares the life out of me just thinking about the range of considerations involved in a tip-based service sector!
Having said that, the fact that the whole restaurant industry in the UK seems to have adopted the 'already included, but notionally optional' tip (usually 12.5%+) to their bills, as well as then leaving space for unsuspecting punters to tip further ('Add gratuity?' etc on Chip & Pin machines when paying), is in many ways worse.
It's a difficult balance: either being able to punish sub-standard service at every opportunity, but only by creating a complex, sometimes pressurised environment (i.e US); or, being within a system where probably only the worst incidences of sub-standard service are punished, but which largely excludes a situation where public judgments are being made by every actor at every turn (i.e UK, most of Europe, Japan).
The 'Curb Your Enthusiasm' Christmas tip episode is great, though!