Tires are wearing - 2002 Chevrolet Blazer

Preventing tire wear is about regular maintainence to your vehicle.
You should rotate your tires every 5,000 miles , and keep
your tire pressure at factory pressures as indicated by the tag
inside the drivers door column.
Alignment is another factor in tire wear , look at your tires carefully .
Look for any unusual wear , especally on the inside of the tires,
as this is usually the most troublesome spot.
As vehicles age , the springs lose their tension to a degree.
This causes a problem in the tire angle called "camber".
The vehicles wheels are tilted inward at the top.
Excessive negative camber will wear the inside of the tire.
Most vehicles can have this corrected by properly aligning
the vehicle .
Another wear problem can be caused by the toe adjustment
being out of specifications .
This is the most destructive angle to tires , it the same angle you use to steer the vehicle left and right .
It normally causes inner and outer tire edges to wear rough in
one direction smooth in another while rubbing your hand around the
tire.
Both these angles can be corrected by a professional alignment .
Be sure the technician inspects your front end for any worn parts,
as aligning it with them is a waste of money and time .
Always ask for a before and after printout of your alignment.

Did you ever see the statements in the tire dealer shops stating a specific tire model will last approx. 50-75,000 miles/
This will never happen unless you have your tires rotated every 7500 miles, the front tires wear excessively compared to the rear tires in 90% of the cars/trucks.
Why? Because the front tires in most cases are the drive tires(front wheel drive) causing the front tires to ocasionally spin causing excessive wear and also the front tires are the ones that guide your vehicle down the road, when you turn the steering wheel you are turning the front tires to make the car go in the direction you want thus causing more excessive wear to the front tires, in order to get even wear from front to back tires one must move the front tires to the back tires at 7500 mile intervals, making sure the tires only get rotated to the same side of the car each and every time, if you move a right rear tire to a left front position, severe damage may occur so please keep them same side rotations.
Also have your wheel alignment checked at a tire shop each time you bring it in for a wheel/tire rotation as pot holes, hitting curbs,etc all can effect the way the tires wear if the alignment goes out.