Hi anotherbreed,
Snap to zero crossing is always enabled when you are zoomed out. If you click anywhere on the waveform and then zoom in, you will see that the cursor will always be placed at the zero crossing (this includes the start and end point of any selections you make). If you zoom in closer to the point where you can see the individual samples then the snap behaviour is disabled so as to allow the user more precision in their selection points.
Regards,
Ben