I get a text a couple of days before to remind me of a (private) dental appointment but I don't have to respond unless the other part of the message is relevant. There is a fee associated with a missed appointment unless they are informed of the cancellation at least 24 hours (on working days) in advance.
The practice also has NHS patients - They warn that not turning up for an appointment without sufficient notification will result in the patient being removed from their NHS list.