The trend of restaurants around me is to just have a single png scan of their menu and nothing else. I was talking to one owner and they were wondering why their SEO was so bad
The template sites are obvious because the owners chose a feature-filled template with all of the bells and whistles but have no use case for all of the frills. There are empty carousels, tons of extra white space, empty link slots, and a halfway responsive mobile experience.
Considering the above, a static, zoom-able HQ image of the menu is not a bad option. It's not optimal, but it's not bad. It tells the restaurant's name, phone number, business hours (possibly), address (again possibly), plus the entire menu. That ticks all of the major boxes for information that a customer may need.
I suspect it just became a sort of arms race with everyone competing on sizzle rather than usability.
What you're describing is pretty much small businesses everywhere. Presumably this is a lot of Squarespace's target market.