Running a small business is having lots of loose ends to manage by only one person. The restaurateur spends all day doing kitchen and front of house, closes the restaurant, and then looks forward to bookkeeping. They’re responsible for HR, payroll, scheduling, and marketing. They have to supervise repairs to the physical plant. Often, they forget which service you need to update to change the hours, they don’t realize that Yelp has changed their phone number to a GrubHub number until they’ve been receiving advertising bills, and even then maybe aren’t sure why it’s so expensive, etc. There are hundreds of companies trying to take advantage of you depending on the limited time you have to dedicate to everything. Why do I get so many “ads” that look like invoices? It must be an effective technique.

> Is keeping this stuff up to date actually difficult.

They usually have a zillion things to do, and this has a very low ROI. The impact to their bottom line is negligible whether they update or not. Not many people will refuse to use their business because they can't bother to update Google/Yelp/etc.

They usually do it if there's a permanent change in hours, though.

I don't know about that. Not that it's easy to measure. But I feel that if I go to a restaurant and it's closed outside their normal hours inexplicably... I am definitely less likely to come back.