Why are some NDBs not displayed on Low Alt Enroute Charts?

Jim Macklin wrote:
Don't know, don't have that chart.

My web site reference now has the official FAA form for Petis NDB/INT in
addition to the Jeppesen Charts.

It is charted on the area chart, but not the enroute chart, because it
serves several STARs.

If you've never seen the source document for a fix, you might find it of
some interest. It also documents the holding patterns authorized for
ATC's use and whether a pattern is to be charted.