This is true, but go ask Nate Silver how that went for him in 2016. The general public has only superficial familiarity with even basic statistics. 60/40 is perceived by many as a near guarantee. More than enough to make them cry 'stolen election!' if the election does not go the way they want.
Market dynamics are subtly different than statistics of traditional polls, since you need to account for fees and slippage and irrationality. You’d also need to compare this to a poll asking “who do you think will win the election?” which is a different question from “who are you voting for?”
"Subtly different"? It's not even remotely the same thing, all they have in common is that the unit is %. The betting probability is the (expected) chance that a certain candidate wins, while polls measure the % of population that votes for a candidate. A polling lead of 20% would seal the election.