It's the expense to cost ratio. They try to decide what their exposure is for selling insurance to the cost. Because no one knows if there will be an SBI this coming season, and that to race in the SBI Worlds you have to have raced this current season, and then pay your entire expenses for the coming year, (Key West is technically the first race of the season, not the last), the cost could be (my wildass guess) $40K or $50K for a team like Geico. Total equipment fees for the year, year membership for everybody on the team, entry fees for the three events at Key West, etc.
Some bean counter at Geico decided the exposure wasn't worth the cost. They will get similar exposure in Englewood for 1/10th the cost.
Except this year the Red Tide is not looking good for spectators.