Shrug, it's a way to bet on election outcomes. No different from betting on football or the stock market. The betting lines really do tell you something about the underlying reality, since if you are sure the true odds are different, they give you a way to turn that knowledge into an expectation of cash. I don't participate myself, but you could interpret that as a weak belief that the current odds are about right.
That particular one comes with the stench of crypto but the original one (Iowa Electronic Markets) didn't have that. Of course I'd expect the offered odds at all those things to be the same, or else there is arbitrage available.
The "accuracy" section claims that from 1988 to 2008, the IEM outperformed polls. It doesn't say about post-2008 so maybe there is more gaming of the markets now.