Because sometimes, companies don't have headcount, for every 1 perm staff they hire, they need to justify (sometimes all the way up to CEO level) why they need to hire this 1 perm person.
I say contract in Singapore is very deceptive.
Because i have seen people get 3 year contract (with full perm benefits)
Or people who get 1 year contract, but with the same company and job scope for the past 5 years (with full perm benefits)
I have also seen people on permanent roles who got retrenched, or who did not "pass" probation
But since we are Singapore, we are "trained" to think that contract = bad, perm = good.