Many restaurants, in addition to the dinner crowd, also service a more business-oriented clientele during the day. Wifi might be more necessary for working lunches, which laptops/tablets instead of phones are necessary.
This is probably one of the most infuriating things in the work culture in Anglo North-America
More seriously, I like lunch meetings. I'd rather get out of work and back to the family an hour earlier than spend it idling with co-workers.
And often times, there's really not a good place to meet. Why drive 10-15 minutes, find parking, etc. at the nearest mall when you can walk down the street to the nearest restaurant in 5 minutes? Plus, I'd never invite a potential client to a mall plaza, esp during the summer...