I think that there's two things that the restaurants hate -
1) It costs them money which eats into their already thin profit margin.
2) It makes it harder to build a relationship with the customers since the customer has to opt-in to giving their e-mail address to the restaurant which they're less likely to do compared to being asked for an e-mail address if you're making a booking directly with the restaurant. Having e-mail addresses for customers is clearly valuable for a restaurant for the purposes of marketing and using things like special offers to increase demand during slower periods of the week/month/year etc.
3) If/When opentable breaks, they've got no access to their reservations - a problem you don't have with a traditional paper reservation book. You probably do have chaos though, if you're a busy restaurant!
> Having e-mail addresses for customers is clearly valuable for a restaurant for the purposes of marketing and using things like special offers to increase demand during slower periods of the week/month/year etc.
And that's exactly why you have to opt-in. Imagine the size of your inbox (or spam folder) if every restaurant you've ever been to had your e-mail address.
I can only tell you my experiences which might or might not be relevant since restaurant culture in the UK and the US is quite different to begin with.
In the UK there isn't so much the mid range large chain restaurants outside of a couple of chains which largely cater to the office lunch-time crowd (such as Itsu or Nandos type places), the possible exceptions being Pizza Express, Cafe Rouge, Strada and Carluccios which are well positioned in both middle class residential areas and office areas for both the sit-down lunch crowd and the evening casual dinner crowd.
I would say that the mainstay of midrange dinning is almost certainly the upmarket pub or gastropub which are often independent or semi-independently managed (they might be affiliated with a larger brewery chain, but the chain doesn't dictate things like the food they serve), and they're the sort of places which would most like to keep in touch with their customers. The bulk of their customer base is almost certainly pretty local, and has already expressed a willingness to spend money their, and being local they're also easier to entice back in with special offers.
A fairly good example would be my local which was launching a new menu back in November of last year. To trial their menu they sent an offer out on their mailing list offering a free dinner (starter and main, not including drinks) from their new menu to anyone on the list who made a reservation during that week. While it clearly cost a not insignificant amount of money to run a promotion like that (probably equivalent to $50 per head were they charging menu prices) it also gained them practice in preparing their new menu, high quality feedback on the new menu, and a certain degree of loyalty towards the establishment as a whole. The later in particular is no mean feat for the area in which I live which is both affluent and quite foodie.
I can think of several local restaurants and several national chains that do. In fact I'll bet most national chains do. I actually get a nontrivial amount of value out of local places' mailings, especially around my birthday when I'm in free lunches, coffees and desserts for a few weeks. Some places do send low- (or no-) signal newsletters but it's easy to unsubscribe.
1) It costs them money which eats into their already thin profit margin.
2) It makes it harder to build a relationship with the customers since the customer has to opt-in to giving their e-mail address to the restaurant which they're less likely to do compared to being asked for an e-mail address if you're making a booking directly with the restaurant. Having e-mail addresses for customers is clearly valuable for a restaurant for the purposes of marketing and using things like special offers to increase demand during slower periods of the week/month/year etc.
3) If/When opentable breaks, they've got no access to their reservations - a problem you don't have with a traditional paper reservation book. You probably do have chaos though, if you're a busy restaurant!