1.Ideal for 4WD vehicle 

2.Lower cost to purchase compared to say a caravan, trailer or motorhome

3.More likely less fuel costs compared to say towing an RV

4.No towing if you choose not to

5.No extra registration costs as you are not towing a vehicle requiring registration

6.You can tow something like a jet ski, boat or motor bike trailer if you choose

7.Some models allow for bedding and pillows to remain in the tent when packed or closed for travel

8.Normally there are no poles as internal struts support the tent

9.You are off the ground and away from any dangerous animals or creepy crawlies

10.An even sleeping surface and no rocks or sticks protruding through the floor

11.Some models of roof top tents extend out providing shade beneath

12.Other models provide an annex or weather skirt for additional living/privacy area and shade

13.You can travel with a roof top tent virtually any place your vehicle can go

14.Less storage space required at home compared to say a caravan, trailer or motorhome

15.Set up is quick