Oil seals can leak and saturate the shoes. Happens all the time on big trucks. Only rakes a minute to ascertain by getting under the unit and looking at the edges of the drums and/or backing plates. If either are wet (showing oil), seals are gone and shoes need replacement. Dry brakes don't work well with oil soaked friction material.
Seals get old and brittle after a time and it's an '02 so it's probably time. Good news is seal replacement is inexpensive and so are new shoes.