Tire rotation spreads wear evenly among tires, which in turn evens tread life. This results in a uniform tread depth on all 4 tires. Better tread wear and tread depth improve overall vehicle performance, including braking and cornering. Even wearing of tires is important for balanced vehicle handling
Tire rotation is necessary if you want your tires to last as long as possible. Rotating tires equalizes the wear that tires receive. If you opt not to rotate your tires, that's fine, but you'll likely end up buying more tires in the long run. And tires are expensive
