There is no thumb rule that you need one or not but it is always better to have one with you.
In past I have never seen any case where lawyer really helped except in case of madman, where his lawyer asked if the applicant can come next day to produce some extra document. Other than that I have not seen anywhere any lawyer helped at the time of interview.
But for moral support I would say yes have one if you can afford. In most of the cases where your employer had lawyer for your case, lawyer is bound ( not legally but ethically )to be present at the time of interview.
Also I have not seen any case where case was denied and lawyer was not there. So its up to you, It is like bad auto insurance policy on your old car, you may not use it but its better to have one just for the hack of DMV.
In nutshell "Yes" but don't ask me $$$s
