Regarding use of single column as primary key on partitioned table

Hi Team
test=> CREATE TABLE public.bet (
betid int4 NOT NULL,
externalbetid text NULL,
externalsystem text NULL,
placedon timestamptz NULL,
createdon timestamptz NULL
) partition by list (placedon) ;
CREATE TABLE
test=> alter table public.bet add primary key (betid);
ERROR: unique constraint on partitioned table must include all
partitioning columns
DETAIL: PRIMARY KEY constraint on table "bet" lacks column "placedon"
which is part of the partition key.
test=>

Can't we use primary key on singal column(betid) on partitioned table
rather than using composite key (placedon,betid)?

Regards,
Durga Mahesh