Why no stations between Jersey Ave and PJ?

The Monmouth Jct "shelter" still exists, but is in a pretty sad shape. I don't recall seeing any remants of Plainsburo or Deans station areas, but the Adams station is still easily recongonizable. There are two sets of stairs that come down from that overhead bridge, on each sides of the track. There are even a few old lamp posts going up the stairs. At the bottom of the stairs on both sides of the ROW, there is a concrete area, although largely overgrown and taken over by weeds and dirt, but still easily recognizable.

This is just east of the Adams Amtrak MOW base.