Older people are hesitant because traditionally before the internet, for sale by owner homes had a bad reputation(iffy homes sold by cheap asses with hidden issues) and the real estate agent was the best choice for most.

I was helping my parents sell they're home and get rid of those con-artist real estate agent....they acted as though I suggested crazy talk for months on end to do for sale by owner.

Lastly some seller agents will refuse to visit or show for sale by owner as a professional courtesy issue(protectionism).