When renting from Hertz..do I have to tell them where I'm going with the car?

I never tell them, they never ask. They probably have GPS tracking on the car so they don't have to ask. I wouldn't put it past them. Those systems are cheap and easy to install.

Their rental prices are probably based upon an average driving distance of 200 miles a day. Many, many years ago, when you rented a car, you paid a base price per day PLUS about $0.10 per mile driven.

They've probably learned that the average miles driven per day was about 200 (some of course drove more, some less), so they just added $20 to the daily rate to make it easier on themselves. They do check mileage just for statistical analysis of vehicle usage so they adjust the daily rate as needed.

Generally you are free to travel in whatever state you rent the car in and any adjoining states. Kansas is not an adjoining state to Michigan. There could be a GPS in the car that tracks where you go or you could get in a wreck and find yourself in violation of your rental contract.

They own the car, so you have to answer every question they ask. Michigan to Kansas shouldn't be a big deal, but it makes a difference if you want to drive into another country.

They have no business knowing what and where you are going or doing.

Some companies have been caught keeping track of how fast the car has

been driven and how the car has been treated.

I've never had to tell them where I'm going when I rent a car.