I'm a motorcyclist as well and I too tend to ride quite defensively. Another reason to avoid the centre of the lane is that the arrow markings tend to be slippe

I'm a motorcyclist as well and I too tend to ride quite defensively. Another reason to avoid the centre of the lane is that the arrow markings tend to be slippery at times - especially on wet roads. The biggest factors, though, are the ones you mention - to be visible in the mirrors and to avoid fluids that have leaked from bigger vehicles - which usually is in the centre of the lane.