If everything in a transaction goes well, the realtor does look somewhat un-necessary. But when thngs start to go south, everyone looks to the agent to fix the problems. It is probably true that the better the agent, the more un-necessary they appear.
FSBO transaction can work smoothly and save the seller some money, but if there is a problem with the loan, or title, or cold feet, or enything else, an agent is sure a welcome addition to the party