Manager listed as additional insured

I have been an agent for several years but fairly new to property management.  Our standard Ga form for the management agreement ask the pwner to list us as an additional insured on their insurance policy.  I've had an owner balk at doing that.  I have my own general liability and there would be no cost to the owner to list me as additional insured.   Am I making to big a deal of this?  Any thoughts or ideas?  Thanks!