Overtaking another bike

I'm riding back from Port Waikato and catch up to another bike where there is a series of corners before the bridge. The rider makes no effort to let me pass and keeps riding maybe 1-2 metres to the left of the centreline.

So was he not checking his mirrors, or just couldn't make the effort to move over?

This has happened quite a few times this summer. I expect it from Harley riders, but to be honest, most of them have been great and let me past.

Overtaking another bike