Yes and No, you don't necessarily need to buy a tent footprint for your tent, but it will help protect the bottom of your tent from sharp rocks or sticks, pine sap and dirt.
You may also want to buy the tent footprint if your tent is able to be set up as a fast fly tent. Then you would be able to use just the footprint and fly, without the tent for a light weight summer camping option.
If you don't purchase the tent fly, you may still want to put something on the ground to protect the bottom of your tent, such as garbage bags or a thin sheet of waterproof plastic (tyvek tent footprint / ground cloth).