Drum brakes are very different than disk brakes. Also rear brakes are generally smaller than front brakes since the front brakes do about 80% of the work of stopping a car. Yet, rear brakes do wear out. I had a '98 Volvo wagon that simply ate up rear brakes like every 10K miles, so some cars do go through rear brakes quickly.
You got the car at 135K miles and the only way to know the condition of the rear drum brakes is to pull the wheels, pull off the drums, and visually look at the shoes and drums. Since you got 15K more miles from them they were OK then, but now the shoes are getting worn. In the old day shoes had rivets to secure the brake material to the metal base of the shoes. When you wore the shoes down to the rivets the metal rivets quickly scored the drums beyond repair. Drums that are not damaged can be turned, smoothing the surface. But you can only turn a drum maybe 2 times at best then they need to be replaced.
If you learned you needed new rear brakes because you were getting grinding noise from the rear brakes then new drums are likely needed. If no grinding perhaps the drums have been turned before and are now thin, or perhaps the garage simply wants to sell you new drums.
Another part of a good rear brake job is dealing with the wheel cylinders. They need to be either replaced or honed smooth. If you don’t hone them properly the wheel cylinders can leak brake fluid, which contaminates the shoes and you have to redo the job. Some shops don’t like to hone cylinders and just replace them.
The last element with drum rear brakes is they also are your parking brake. This is a mechanical set up and it adds to the job when parking brake parts are bent and rusted which is very common. All this adds to the labor. So, labor costs to do rear drum brakes is about twice as much work as a simple pad/rotor replacement on front brakes.