Because:
1. Restaurant managers and chefs are not web designers. They are kinetic hands-on people who work in the concrete world.
2. They either try to do it themselves to save money, or they hire some stupid snowjob PR/communications person to do it for them. The PR/communications person convinces them that bells and whistles are needed to 'establish the brand' etc., which helps them seem more valuable and allows them to charge more. "Look at the fancy site I made for you!"
3. They don't have time to deal with this and it doesn't seem important to them. You can hardly find a more brick-and-mortar culture than in restaurant work.

I've been visiting a couple US restaurant websites lately and it's very odd but once the restaurants close the domain becomes a not-very-obvious spam/link farm. like it still has some design and branding but it is a spammy landing page. it's odd to see it twice. maybe someone picks up the domain after it expires and goes to that extra step of not making it very obvious, or just gets it as part of the liquidation process, not sure

That said restaurants do have documents and things they use interally (I made a website that spits out a menu from an excel wine list and I don't remember how the food list was updated, it was wordpress based) but the issue isn't even that the sites aren't updated and dynamic but what that is there is awkwardly flashy. I think it's because they don't know what a good website looks like so just want the digital version of a TV ad or print ad

like it still has some design and branding but it is a spammy landing page. i

Is that because they just love love love to use frames? Seems like it could be.

Now that I've finally RTFA I'm gratified to see it's the long version of what I said. Although I think chefs are actually really disinterested in their websites, generally. I would put 95% of this down to the PR people, who are the ones trying to "extend the brand" to an online experience.

Fancy hotels actually have the same issue, though at least you can usually use them to make a reservation.

Here's a good example of a terrible restaurant website. It's not even a fancy place, just a somewhat upscale pizzeria. (Warning embedded music).

It is funny that most other businesses have gotten past the all flash, animated website with embedded music phase of webpage design but restaurants are in some sort of early 2000s time warp.

here are the sites I'm thinking of

altorestaurant.com
ivyrestaurantgroup.com

it's very odd because when I went to the ivy restaurant site I thought the restaurant was still open so it was odd for me to figure out what was going on. there's some plausible copywriting but i finally realized something had 'happened' and then googled to see it's closed

2. They either try to do it themselves to save money, or they hire some stupid snowjob PR/communications person to do it for them. The PR/communications person convinces them that bells and whistles are needed to 'establish the brand' etc., which helps them seem more valuable and allows them to charge more. "Look at the fancy site I made for you!"

No PR/communications person worth their salt would recommend a flash-heavy site to establish a brand nowadays. It is really bad for mobile and SEO. A friend of mine (a user interface web designer) just posted on Twitter that in his experience restaurants won't listen to the counsel of professionals that these types of sites are a bad idea, and they shop around looking for a designer that will do what they want. Restaurants owners/managers WANT this shit. So as a web designer either you do it or you turn down business.

Restaurants owners/managers WANT this shit.

That's kind of what the article says--that restaurants think in terms of giving the diner "a total sensory experience" and think the web site should do the same thing.

What I got from the article was:

Restaurant owners have no clue about the internet or web sites. So they throw a lot of money around. And they get the wrong designers for what they need. But they look at the product and say, oh how pretty. And ignore it from there.

This one isn't too bad. At least you can find a menu. And it's a great place to eat.