Making it easier for me to lane-split on the other hand is not required of the driver. If they are doing it, they are doing so entirely optionally and consequently it is evidence of their being considerate.
When lane-splitting I appreciated the move over for the following reasons:
* I know you can see me
* It is more comfortable with more space
* I know you are willing to look out for other motorists => if a thing happens unexpectedly right in front, the spot I'm in next to you is safer than standard.
On the flip side, when _I'm_ the one on the bicycle, and some car goes half out of the lane to pass me, I think "geez, you don't need to give me 20 feet of space, I'm not some drunk idiot, I can ride my bike in a straight line!"