Why is there no option -U with pg_dump?

Why is there no option -U with pg_dump?

when i call psql i can connect as another user and i usually dont
need a password because i trust all local users via hba.conf, right?

thats the way it works on my host. but why cant i connect via pg_dump?
i need this because every devolper gets his own database and
sometimes a developer wants to mirror the production database. i
tried to write a little shell script which drops and recreates your
user databse and then uses the dump of the production database to
create schema and fill teh rows. useful option is --no-owner to
supress the connect statements.

But i cant connect without user input. because the option -U ask for
username and password.

Any workaround or suggestions?

janning