Most shops do not do a true brake fluid flush and frankly a consumer should not expect one even if they ask for one. What typically happens, in my experience as a service advisor and technician, is that a technician will hook your brake line system up to a machine that removes all the fluid and replace it with one quart of fresh fluid and the remainder, if applicable, is filtered remnant of the previous fluid.
That is not a technician or service department being lazy or neglectful, it is all that most mainstream auto manufacturers require. The reality is that most people do not want to spend more time and more money to do a true, full brake fluid flush and replacement and doing what I described above is more than adequate for the performance of the brake system with the majority of vehicles.