You are right they are still around for a reason, but not the reason you seem to imply here.
The betting shops take money from the left and money from the right, weigh the amount of money held for each entrant to form a price that they will accept more money at, keep a commission on each transaction as their profit and therefore win regardless of the actual result.
The price does not reflect any opinion they may have on who will win, it just reflects who the punters think will win.
I note the betting shops don't specify the next president as being the person who is inaugurated next January, as this race could get messy in many ways after election day. They seem to have differing criteria about who they will classify as the winner. Be very cautious in this market as you may think you win, but may not get paid out - read and understand the fine print.
My personal view is that is highly unlikely Joe Biden will be the next inaugurated President.
