Or maybe you see a deliberate provocation where they are just trying to stay safe or there's some reason why it's not possible to do otherwise.
On topic of riding too far to the right - there's plenty of reasons to do so:
- if there is any grave or small debris at the edge of the road (that a car driver wouldn't even pay attention to, but can be deadly on a bike)
- if there are cars parked in the bike lane (you either risk dooring, or you need to duck in and out making it way more dangerous)
- or just to stop the driver from overtaking you, when there's oncoming traffic and you know that the 3 of you won't fit side by side, but the driver still insist on trying to overtake you as if you were stationary fixed object)
Just as you would prefer to be given some extra space in a plane when it's a rough day, and you may not be able to stick to the hemispherical levels, the bike rider may require extra room on a rough or dirty road. Even if for the car driver or RPT pilot the road / air is perfectly fine (or just with small bumps).
I won't say that all bike riders are flawless and follow the rules perfectly, but neither are drivers.
And I think the comparison between ultralights and bikes is very solid - both are perfectly valid users of their space (either road or airspace), both have some rules not apply to them or some restrictions lifted compared to other and both are very vulnerable next to bigger vehicles sharing the same space.