That good ol' symbol of the culture of professionalism--the "business lunch"--is actually a quite pernicious and invasive practice. Eating out with someone should be an enjoyable, relaxing event with a friend or with a group of friends. In the tradition of the "business lunch," it becomes an extension of work--I'm sorry, "career advancement"--by other means.
Often, maybe even usually, the "business lunch" is not a meeting of peers, but a meeting of some one person who has something the other person wants and is using the lunch to 1) get that something or 2) cultivate a professionally useful relationship. The subordinate must swallow her or his food carefully, order non-embarrassing food (spaghetti with any kind of red sauce, for example, dangerously risks blotches on the uncomfortable suit the hapless diner has to wear), watch his or her words very carefully, and be wary of how much one drinks.
Of course, heaven help the waitstaff if there's a slight problem with the meal. And heaven help the waitstaff if the "business colleague" one dines with tips only 5% (if at all), especially if the strategic architecture of the restaurant is such that it's impossible to inconspicuously slip the waiter/waitress some money on the way out without the honorable, professionally useful "friend" seeing the transaction.