If this is the indented use case what purpose the coffee shop have to add one? If in most cases it'll only discourage customer attendance.
To be a member of the queue of an establishment can carry some of the social status of that establishment itself. This is a primative notion yes, but fairly ingrained culturally. As businesses often judge their prestige by the length of the queue to enter.
Too long of a queue could discourage customer attendance as well, as people may not want to wait a long time, no matter how prestigious the business is. In addition, a lesser-known business could use lower wait times as a competitive advantage.
What really matters, in my opinion, is whether having a long line during certain peak times generates more revenue for the business (by being able to charge more, or by gaining attention due to its long queues) or whether providing a faster and better customer experience with shorter wait times does (and perhaps more customers during non-peak times)
Whether one is better than the other may depend completely on your business. Also, I'm not sure this technology forces you to publish your current density information. You could simply use the information for business intelligence gathering and for providing promotions during non-peak times.
To be a member of the queue of an establishment can carry some of the social status of that establishment itself. This is a primative notion yes, but fairly ingrained culturally. As businesses often judge their prestige by the length of the queue to enter.