But you don't know what advances would happen in 40,000 years, that too on another solar system. Maybe alien kids would be playing in their back-yard beside their Oort cloud equivalent and might check out Voyager just for fun.
I've always viewed the Golden Record as a way to make humanity feel better about its future. The need to leave a legacy behind is core to who we are, and that's exactly what we did with those two discs. We left something behind that will survive for 1 billion years, with the infinitesimally small hopes that someone will find it. But, it makes us feel good.