Why do databases require a separate user account when installing?

Question

When I install PostgreSQL in Mac OS, I need to create a user named "postgres' in order to install the DB. I think the same thing applies for many other DBs in Unix. So what is the reason that we need a new user for installation?

Answer 1

Because it's good idea to run different things as different users so that if somebody breaks in through a security hole in one program they are limited in what they can do to the things that the user for that particular service can do.