I've heard of realtors who simply give out showing codes & instructions to their clients and send them, unaccompanied, to see properties but until this year, I hadn't experienced it with any of my listings. Earlier this year, a single family listing I had in Pembroke Pines, Fl. was under contract. The list agent's wife gave the prospective buyers the code to the lockbox so they could see the house once again (note to self: once it's 'pending', remove keys from lockbox). The neighbors called me, quite upset, to tell me that the prospective buyers were at the house washing their car! I rushed over to the listing & sure enough the buyers were inside looking over the premises alone (they had been testing the water spigot). I asked them for the house keys & made sure they left. Within 2 hours, I had a locksmith at the house re-keying the place, I'd managed to placate the neighbors & informed the buyer's agent that I expected to be reimbursed by him for the $200 cost for re-keying the place (I was).
Yesterday, something similar happened: the owner of one of my rental listings called to tell me that a lady came by the house to see it, unaccompanied. Her husband had seen the property the previous day with their realtor & now she wanted to see it. My client was perplexed about why the realtor wasn't with this lady. I told him that he doesn't have to show the property to anyone that shows up without professional representation.
I can understand not wanting to spend time showing other agents' rental listings or re-showing properties to the same people. But isn't that the job?