Why do landlords take a deposit

The basic intention behind a landlord asking for a deposit from the tenant, is usually to encourage the tenant to properly look after the rental premises and deter them from causing damages to the rental premises.  If the tenant causes any damages to the rental premises during the tenancy, the landlord, as per the terms of the rental  agreement is well within his/her rights to deduct the appropriate repair costs of such damages from the rental agreement.