Hi,
Two possibilities:
- The tires are directional. Check for arrows as other posters noted.
- Old ideas die hard.
On the second, when radial tires first hit the market, it was recommended NOT to change the rotating direction for fear the belts could separate from the cords, based on the idea the belt/cord system essentially "took a set" that would be upset. Radial tire building technology advanced to the point where Michelin said "cross rotation is ok" in the mid-'70s or so, and most other mfrs followed suit shortly thereafter.
Still, 30 yrs later, you'll hear the belts will separate and blah, blah. Personally, I prefer to cross-rotate, and, if there's a full sized spare on a matching wheel (as opposed to the "black steel spare vs shiny alloy road wheels" we often see), use a five tire pattern. So far I've noticed nothing negative about this drill.
Now, it's well-established that tire inflation pressure has more to do with radial tire failures than most any other influence, so I WON'T say that an underinflated, cross-rotated tire MIGHT not fail sooner than one rotated only front-rear and also similarly underinflated, but I haven't found anyone willing to test that theory for me!
Rick