If you’re in a country that drives on the left, you’ve probably noticed that the right-hand side of your tyres wear more quickly. You’ll notice it more if you have a powerful sports bike and you’re accelerating hard and leaning a lot in the corners, but even cruisers with fat tyres experience it.
There are two reasons.
The road slopes off to the left so that water drains from the crown of the road (where the centre line is) into the gutter or onto the verge. This means that slightly more of the right-hand side of the tyre is in contact with the road.
Under acceleration and braking, more force is transmitted on the side that has the most contact with the road.
You can see further through a right-hand bend, so the temptation is to ride faster through it. There are also many roundabouts which create a right-hand bend which is longer (and more cambered) than it would be if it were simply a right turn.
On a regular road, the camber is often to the inside corner, not ‘adverse camber’ where it slopes away to the outside, but on roundabouts, the it’s usually adverse camber, exacerbating the wear.