what function or purposes does it serve amongst the living

The Haitian zombies were related to the people’s status as slaves. A zombie was supposedly a dead slave who had offended the Voodoo deities in some way, and was therefore brought back to life to continue working as a soulless slave, instead of going to a heavenly afterlife. So originally the fear of zombies was more a fear of becoming one, than being attacked by them etc.

what function or purposes does it serve amongst the living

Story telling, books, movies, comics, games

I suppose zombies are a reflection of the loss of individuality and a reversion to a primitive state of nothing but feeding. Newer zombie tv shows does have people coming back from this state and having to live with the consequences

half interesting read

https://en.wikipedia.org/wiki/Zombie

transition said:

half interesting read

https://en.wikipedia.org/wiki/Zombie

Agree, very much worth a look.