NO REAR BRAKE CHECK DURING SERVICE

Not even a month after my Renault was in for a service at DTM Renault in Strand, I get my wheels balanced and rotated. They show me that my rear brakes are basically non existent. Why did Renault only advise me to replace my front brakes? If you didn't check my brakes what else did you not check? Why do I even pay for a service at Renault if they do it half? I can do it for so much cheaper at other places but thought I should do it at Renault so they can do it properly. I think they try and fit in too many cars a day.