According to Michael Bauer,
executive food and wine editor and restaurant critic for the San Francisco Chronicle, restaurants as a rule of thumb when turning reservation tables, should allot 90 minutes for a table of two and 2 hours for a table of four. When diners take longer than this and the table is supposed to be turned for the next reservation he makes a good point: Restaurants need to communicate to the table and the incoming reservation what the situation is and never "call-out" the table that is hopefully on the way out. You think this is common knowledge to management and staff but you would be surprised how many restaurants forget about what is fundamental to their success; customer service--->communication. Not sure which is the cart before the horse but I presume both can be interchanged with one another.
I've worked in the service industry long enough and on the other side, have dined at many restaurants to know people don't appreciate being rushed. But on the other hand, diners needs to be more aware and cognizant they may not be the only ones occupying the table the rest of the evening (or afternoon if it's lunch).
For the most part, dinner, wherever you are, should not be rushed. Whether you're at home or in a restaurant it is a moment in your day where you can sit still and relax, share stories and reconnect with the people you love and be thankful for what you have. And if you are fortunate enough to have the option to eat with someone, you must never eat alone (more on that later).