Seems to be back today. Just checked a handful and they're all showing the Area Served again on desktop. On the mobile it just says "Serves" and I can't remember if it used to have "area" on mobile phones.
"We found that business profiles with missing service areas are the result of a technical issue. Our engineers are working on the issue but they don’t have an estimate for when they'll be able to resolve it."
An update from Google about missing service areas - sadly a bug with no estimate for fixing.
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