Can a Plot Become Obsolete?

TOF has a soft spot in his head for taxonomy.  When he was younger and maintained a sort of library in his basement - and his milk-cousin still remembers how TOF charged her an overdue fine on a book she kept too long - TOF began to notice structural and thematic similarities among the SF stories he devoured.  [Some of those books still have bite marks; but the fantasies were hard to swallow.]

Galactic empires, decline and collapse of. 
Time travel, serial closed loop. 
Alien contact, hidden aliens among us. 
etc.
Inspired by the four-letter classification of alien beings in James White's Sector General stories, Young TOF set about taxonomizing all of his SF books and short stories with 4-letter codes.  The details are now thnakfully lost in the mists of time, but the first letter was a broad overall category, such as the aforesaid galactic empire; the next level, a detail within that category, such as galactic empire in decay; and so on.  The whole thing eventually was set aside.  Was a story about an alien galactic empire classed under Aliens or under Galactic Empire?  Still, TOF could not shake the feeling that there were underlying structural similarities among groups of stories.

Later, it turned out he was not alone.
Enter PoltiGeorges Polti (1867-1946) was a French writer, critic, and theorist - and what self-respecting French litterateur is not a theorist? - who possessed a masterful command of the theater.  Based on a remark by Goethe that there were 36 dramatic situations - and Schiller's inability to find even that many - he set about cataloging and typing them, supplying for each situation examples from ancient and modern theater, occasional novels, and even historical and everyday events.  Criticized by Etienne Souriau for artificially tweaking the list in order to achieve the magical 36, he did not, in TOF's undeniably humble opinion, achieve a true taxonomy, in that the canonical 36 were not apparently organized as to species, genus, and family.  Some indeed seemed to be the same situation, though they may have appeared distinct to those with the sensibilities of an earlier generation.

M. Polti did not claim there were 36 plots.  He claimed there were 36 distinct dramatic situations.  A plot is a series of encounters.  A novel might contain several of these situations; a short story may revolve around only one.   About one of the Situations, the first one, he made the curious observation that:

It is apparent that, in the modern theater, very little use has been made of this First Situation.

Can a Dramatic Situation go obsolete?  Why would this Situation fall into disuse?

We'd tell you (TOF hears you say) if you would tell us what the @#$% this Situation is!

TOF is glad you asked.
Read more »