This is a Bad Thing. Don't put your fingers on the blade. Your skin carries acids that will eat your fingerprints into the metal. This makes blade owners Very Cross. Do not carry ANY blade unsheathed.
Sheaths help to keep accidents to a minimum.
They are a Good Thing. This includes spears, halberds and axes as well as daggers and swords. Know where the end of your sheath is. Don't poke people with it. We must live under mundane law even at a Society event, and you might forget about the blades when you leave the event to go home.