Tires wearing out before time

Just had to have my Michelin 60K mile tires replaced after 33K miles. (205/65R15-94V) Alignment is fine, tires were rotated every 6K miles, even wear. My question is why?
Could the fact that my car idles fast have anything to do with the wearing out of the tires. When at a stop sign on an incline, I have to keep the brake on because the car wants to creep forward. It’s a 94 ES300 Lexus. I asked the mechanic if it the idle could be adjusted and he said it was fine.
I now have a cheaper 70K UniRoyal tire. I don’t understand why this cheaper tire has a longer life tag.

No, the idle speed has nothing to do with tire wear.
Tire wear is affected by several factors, including whether they are inflated properly, and whether the wheels are aligned correctly and the tires are properly balanced. Additionally, a lot of local driving–with frequent turns–will wear out tire treads more rapidly than expressway driving with few turns.

Also, if those Michelins were high-performance tires, they would be prone to rapid tread wear, no matter what the manfacturer’s statement about tread wear might be.

IMO, fwd cars with larger more powerful v6 motors do poorly in tire wear unless driven very conservatively. I feel this combination along with your driving habits has more to do with poor tire wear.

 I would add one thing to VDC's suggestions, include high mileage tyres in the high-performance class for this issue.  You can't make one tyre best for all conditions.

Most tire wear occurs in the cornering mode. The more turns you make - compared the amount of miles you drive straight ahaead - the more rapidly your tires will wear.

Put another way, if drive in the city and make lots of turns, you will get less miles out of your tires than if you drive in the country and hardly make any turns at all! Straight ahead is practically free!

Also mileage warranties are marketing tools - like an insurance policy. It’s easy to promote a tire with a long treadwear warranty - especially if you hardly ever have to pay out on one!

“Michelin 60K mile tires”

Those mileage ratings are pretty much fantasy.
You might get 60K if you drove only on the highway and did no braking or turning.

“Most tire wear occurs in the cornering mode. The more turns you make - compared the amount of miles you drive straight ahaead - the more rapidly your tires will wear.”

I will readily agree and also add that fwd cars increase tire wear under power much greater than a rwd/awd car. The differences cannot be completely mitigated by rotations alone. FWD cars eat tires under power while cornering but conservative driving does much to ease “the pain” of wear as many who drive fwd cars and still get reasonably good mileage from their tires can attest.

This is especially true of earlier v6 models w/o modern traction control devices. It’s the driver who often has the final say in tire wear. I routinely exceed tire warranty ratings in my rwd/awd cars and trucks. I have never done this in any fwd car I have owned. My driving habits and fwd has a lot to do with it.

Thanks for all the input. I do live in the city and do alot of stop and go, many turns from here to there and back. It makes sense that the front wheel drive adds to the wear as well. I appreciate all your feedback. Merci Beaucoup!