I agree with those sentiments, but regarding the latter bit, the restauranteurs doing that must be acting illegally on minimum wages legislation (go by your overview of modest to wages to start off, divisible by working double the contracted hours). The biggest problem those catering staff have...
Always pay by card, but quietly ask the waiter/waitress on paying if the staff get the tip if it's added to the card payment. If yes, we add it, if not, we leave a cash tip.
Unless poor service or a rip-off for what the meal was, then zilch.