Service Really Neccessary Every 5k Miles?

It ensures the most contact at any given time. If you went 5k, rotated, 5k, rotated, when your front tire has been 5k on the front, 5k on the rear, now back to another 5k on the front it gets a chance to wear as evenly as possible. Now, leave that same tire on the front for 10k, then swap it to the back, it will not have the same contact area because it didn't have an opportunity to wear on the back. It will now take longer to even out because it has more wear introduced to it. Yes, at the end of the 20k it may have evened out, but how long have you been driving without max tire to road contact area? Tire pressures also play a huge role in this.
Its hard to explain so I hope that made at least a little bit of sense.

 

I mean my tire guys rotate them for free, aslong as I buy the the tires there ofcourse

 

Thank you so much. That makes sense to me. I knew there had to be some "science" behind it.