That's the way tires wear. WHen it gets too flat, time to replace.
Stock tires suck though. When I get a new bike, I take them off as soon as I get home. What brand are they. I've had really bad luck with Specialized tires. Bought a cheapo at $20, lost a 2 inch chunk of rubber after 500 miles. Bought a $45 non cheapo, lost a 2 inch chunk of rubber after 700 miles.
Had Stock 700X25's on my New Lemond. About 400 miles into the life of the tire, the sidewall split. Put a 23 on the front, placed the Bontrager 25 to the rear. Next week, same split on same this tire.
I use wire bead tires. Continental 2000's (think they are called Race now) were $20, now $30. Seem to wear well. I never use light race tires. Too soft and the rubber wears quickly.