IMO it's really the only compelling argument for HTTPS on sites that don't deal with traffic worth intercepting. Other than that, I agree with you re café Wi-fi, etc: the man-in-the-middle risk is so small and localized that it may as well not exist.
Not only is the coffee shop using an ISP that is likely MITMing you, insecure coffee wifi routers can be exploited at scale to MITM a lot of coffee shops at once.
