Why do I have to be added on the car insurance?

Insurance... please support?
Considering hiring an automobile in the 25th for the 29th
"How much roughly to get a 17 yr-old using a 250 ninja? How about a 600cc bike? I don't have my drivers license nevertheless"I'm currently house shopping and my employer mentioned growing my car  insurance   coverage to protect the price tag on my household I get into an accident where the damages are more than my coverage