You do not NEED to rent a car. There are shuttles available. However, if you are a party of 3 or more, using a town car or taxi would be less expensive. Not to mention you will be at your hotel ASAP to begin your vacation without waiting to unload other passengers at other hotels.
A cab from the airport to SS will be around $45 each way + tip a town car $80-90 round trip + tip, shuttle $28 PER PERSON + tip round trip.
Notice town car and taxi are priced for the ride not per person making them less expensive if you are a party of 3 or more.
Of course if you investigate you can save money off these prices as well (especially taxi prices).