You are assuming the costs to drive the consumer to the website, get the consumer to sign up, and retain the consumer are lower than the commission to an agent.
Few years ago the cost to Geico for each new piece of business was around $240 and their persistency was around 80% thank god they suck
With an average auto policy of $800 @ 12% new that Prog pays, they just saved $96 they would have paid an agent. The price of loyalty