Walking in with a reference gives you an upper hand as it adds a little more credibility to the candidate, which in turn increases your chances of getting the job. As the restaurant knows a little more about you, it established that you will be called only if they think you can do the job thoroughly.
Its important to obtain clarity on what the actual requirement is. If an advertisement only mention about the requirement for a chef and does specify about the speciality, it will be a waste of time for both the restaurant & the chef whose speciality lies in Chineese cuisine to go and interview for which the actual requirement is that of a chef with expertise in Italian cuisine.
It is highly advantageous to go in an interview with some reference in the hotel industry as the added credibility makes for a easy and straightforward negotiation for salary for both the hotel and the staff.
With recommendation, the recommender places a bet on the candidate, which motivates the candidate to prove his worth to the employer which in turn helps the business.
Especially in the hotel industry, it gets to difficult to meet right people at the right time and get your job done right away without the need to chase after managers who might not be available when you exactly need to see them for queries related to the hiring procedure.