Maybe it's a North America thing, but I can't think of a (purely ICE) car here that has anything smaller than a ~13 gallon tank... Maybe there are a few with 10-12 gallon ones, but they'd be outliers for sure.

For a typical family-hauler that's be used on road trips like a Honda Odyssey, 16-20 gallons is totally common.

Huh, I'm in the SF bay area with a prius (advertised as a 11.9 gallon tank, but due to one thing or another, it's never more than 7 even when beeping at me to refill. But I do agree that pretty much every time I fill up and look at what the previous car used, it's some crazy high number in comparison.