It is hard to tell from the picture but looks like the tread is not worn evenly across from the side to the center. It also looks like it is worn more on the outside than the inside. You can buy a tire gauge and measure each tire block going across the tire. Take the readings in a couple places on the tires. Do this for all four tires. If you have a new spare do this on that too. A new spare will give you what the factory tire would have had.
What rims are you running? How wide are they?
The tread compound on that tire is softer on the top of the new tread and progressively gets harder as you wear it down. You will notice a difference in wear degree as you wear the tire down.