I wonder if some of the restaurant differences could be due to regional variations? Whenever I'm in London it feels like you're 5-10 years ahead on card payments (and don't get me started on Oyster vs Get Me There for transport). Up in Manchester splitting a bill by card can be a nightmare - often the restaurant doesn't know where the card machine is, doesn't know how to work it for anything other than the whole bill, accidentally charges the wrong amount and then the manager comes chasing us down the street for not paying enough... Chains tend to get it right but smaller outfits seem to struggle.

I agree on the merchant fraud thing - anything expensive or might be faulty/fake I buy on card for the consumer protection, and I have used chargeback (or the threat) a few times.