1.   The original intent was to keep out motor vehicles and the land-scarring infrastructure required to support them.  That's why that verbiage was originally chosen.  Other forms of mechanical transport remain allowed.   

2.  Multiple independent studies show cycling impact to be similar to hiking and far less impactful than equestrian use.  

3.  I enjoy the scenery when I ride every bit as much as when I hike.  Any claim to the contrary is self-centered elitism.