To be fair, there have been TV shows that only lasted 2 seasons of eight episode each for a while. I believe John Cleese's Fawlty Towers dates back to the late 1970s.People who bitch about not fucking Nana yet are the reason television series have dropped from five or more seasons of twenty episodes a piece down to two seasons if you're lucky of eight episodes if you're lucky.
No patience or commitment.
I'm not aware of whether it wasn't financially successful enough at the time, or if Cleese just wanted to move on to other things.
Some shows are written as what amounts to a tight weave of stories (or story) without really having room for episodes by a larger selection of writers (The Flight Attendant comes to mind; Game of Thrones qualifies as well, as it was based on a series of books (albeit one that is even now incomplete))
Most of my favorite shows are designed to tell many stories following the same basic format, involving a consistent cast of characters that may have on-going storylines involving them that are usually in the background. I'm thinking of Law & Order, Law & Order: SVU, Law & Order: Criminal Intent; the NCIS shows; the CSI shows; Dick Wolf's FBI shows. However, despite my love of police procedural, I've enjoyed other shows with similar formats. WKRP in Cincinnati, M*A*S*H, Moonlighting (though that involved a bit more story to story continuity in its later seasons, and (i believe) was hampered from completing a full slate of episodes from due to cast issues, more than money or story issues).
I'd be inclined to say that limited season runs and season-long arcs tended to show up strongly when cable channels started making their own shows. The on-going nature of the storyline would drive involvement (where missing any one episode of Law & Order wouldn't be likely to make it confusing to watch the next); limited episode counts would mean that you could pay for fewer episodes, and still have the episodes you pay for showing up in November, February, May, or August (the months where the Neilson organization (possibly Arbitron too) assess the viewership of shows to help set advertising rates).
Please note this analysis of TV trends was tossed together in a few minutes (though based on thoughts I've had for much longer), is pretty much based almost exclusively on American shows, and is limited to shows I've watched; and, of course, is my opinion only.