You are correct on one point... insurance companies are rippin' us off!
Now as for an umbrella coverage, state law requires that all driven vehicles be covered with the state minimums... so as long as the insurance companies' lobbyists keep their pressure on state government, it won't be changing anytime soon.
Edit - I forgot to add... isn't there a provision in the state books that state that someone can self-insure provided that they sign over a huge sum of cash (somewhere in the ballpark of $10k) or is this urban legend? I always wondered if the ultra rich took on this option. This way, all vehicles would be covered under one policy? Still pricey though...