If you search the archive of Pprune you may find a similar thread as this was discussed at some stage of the last year (I think).
In a nutshell, the weight penalty of carrying electric motors to spin up the tyres does not justify the savings on wear. There is also the issue of adding further complications and equipment to the machine that has to be designed and built and then maintained. Simplicity usually wins.
I understand that designers have done many tests over the years on this point. What they found was (again, if I recall correctly) that you have to match the rotation of tryres closely to what they will be a second after touch down. If the tyre is rotating slower or faster than it will be after touch down - it still suffers wear in adjusting from it's speed to the actual one.
Something like that!