One of the reason probably coz you do not have any on-going loans, less one factor to monitor your payment habbit/record.
Go get a Credit Card, nil or minimize usage, but pay on time, SST RM25 give it jer in return for a better scoring.

Btw, banks here don't really quote u interest rate based on ur CTOS score, its mostly based on the property's type, geographic, bank's linkage/panel (if its new project), and ur age, income, networth, or somesay ur job (risk)

CTOS is a reference tool jer

I not sure how it links, but did u file for LHDN/Tax?
It somewhat links ur record.