Yes. There are many good reasons for the listing agent to be there for all showing appointments. The listing agent should know the property better than a showing agent. It may be the showing agent's first visit to the location. The listing agent will have answers to most questions about the property, having listed it, and by having more intimate knowledge of it. The listing agent's presence may also insulate the owner from unwarranted questions from unprofessional agents, and rude potential buyers. The listing agent will also lend moral support to the owner's knowing that their fiduciary rights are being protected right there on site. It also shows that the listing agent CARES. He or she cares enough to be there, it shows that the listing agent is thinking about the client, not just a commission.