There is a real reason for that: no-one works an adjunct because they want to stay an adjunct (or, at least, I've never heard of that). You work as an adjunct because you want to stay on the academic path while you angle for a tenure-track position.

However, since the supply of PhD students grossly outnumbers the number of tenure-track positions, people do end up in some kind of limbo (post-docs, non-track lecturer or adjunct positions) for a long time.

The tenured positions also don't pay as well as industry but they come with much greater freedom, more flexible balance of research vs. teaching vs. service and incredibly robust job security.