And this is because pilots are trained to keep their nose gear on the centerline, and there are relatively few aircraft types in use which receive the "heavy" after their flight number over ATC. So wheels are going to roll over the exact same tracks repeatedly.

> pilots are trained to keep their nose gear on the centerline

Funily I was learning to fly at a grass strip and we were told to vary our positioning left and right on the runway for exactly this reason. In practice it meant that as we were taxiing to the runway my instructor would tell me “Today we are taking off left/right of center to avoid damaging the grass too much.”