Why should the tape on the left side be wearing out faster than the right?

more left hand turns. greater friction when leaning into the curve

Maybe not as good a job was done on the left. Consider it a blessing. Pink is meh.

It's actually braking that's wearing on the tape. I mostly use the brakes from the hoods, and this bike is set up left-rear (for cyclocross), and i use that brake more than the front.

The tape started out as purple, it'll be replaced this winter with a new color. Maybe orange.