Very well said, especially that "bribe" thing is the point. There are indeed some other countries in the world that share this excessive tipping culture with you, actually quite a lot. Where nothing can be done if only the official price is paid without a "tip". The idea to tip to get better service then others is really a very ugly thing and in my opinion should be proscribed.
Having said this, I do also tip nowadays. Not so much on a cruise ship where the jobs and the salaries are good, but when using Grab (same like Uber) for a ride or a meal delivery. Those guys are using their own vehicles to do me a favour for very limited money. Certainly if the price is not so low, I would not tip, also happens. Has nothing to do with bribe as the service is already done and one probably will not meet the driver again in this life.
And about how much tip? I guess there is a very simple internationally valid basic rule, the price of a coffee. Yes, I know, the Russians and the Chinese call it "tea money", the Germans "drinking money" 😄