Several years ago, while riding thru Texas for my first time, I noticed that in rural areas where there are lots of wide open space (most of Texas) and a very wide shoulder, that drivers would pull over when someone came up behind them and drive on the shoulder to allow them to go on by. This would definitely get you a ticket in Mississippi!
Been seeing and doing it as long as I can remember here. It's always been a road courtesy move. Get's a wave or a brakelight tap as they go on by usually
Recall seeing signage about Not driving on the shoulder in some states...as well in a few places here.
There are a few vehicles from certain states that will not do it even if they see it happening ahead of them, nor move out of the fast lane on IH-10 going 5 or more under. Not profiling...sure can count on it to be one in particular more than any others
Don't move over on the bikes often as we do in our 4 wheelers as we seem to be right ahead of the pace, and there is a lot of junk in some spots...unless pressed