Claiming the Depost from DPS

Why does the DPS insist you have your deposit return submission form signed by a solicitor which can cost you anywhere between £40.00 to £100. In my case the amount paid represented more 20% of the deposit amount. If the deposit was paid in on your behalf by OpenRent, they know you, have done the checks. Why can’t the DPS return the deposit via OR who in turn will pay the monies into the bank account registered with them. If OR want to expand the services offered this must be high on the list. Has anyone else had this experience and or agree with the suggestion of it being a free service via OR