Whatever happened to the half hour drama? The last producer to really use the half-hour drama as a form was probably Jack Webb and even he abandoned it eventually. Webb produced the half hour Adam-12 with Kent McCord and Martin Milner which ran until 1975 (and outlasted Lassie by a year), but when Web came to create his next series Emergency in 1972 it was in the hour long form. Since then there hasn't been a half hour long drama network series made for American television.
The half hour drama has a long and storied history. Most drama's in "old-time radio" were half-hour programs. For a radio program to last an hour it had to be special, usually a play created specifically for radio or an adaptation of a theatrical movie on a show like the Lux Radio Theater but even that wasn't always the case. Some daily serials in the "Golden Age of Radio" like The Adventures of Superman and the last incarnations of Yours Truly, Johnny Dollar were as short as fifteen minutes long - with commercials. Just about every other show - comedy, drama, anthology or variety program - was a half hour long.
Most of these conventions survived into the first decade of television. Variety shows got longer, but they were providing a wide range of entertainment, and the stars usually welcomed the additional time. But most of the shows were a half hour in length. The prime time schedule (at the time 7 p.m. to 11 p.m. Eastern) for the three US networks 1956 - the year I was born - shows 28 hour or longer programs, and 81 half hour shows (plus an assortment of shows at odd lengths). Of the long form (one hour and longer) series, 12 were variety shows, 12 were anthologies 2 were sports shows, 1 was a movie. One, Wire Service was a drama with a continuing cast of characters. Among the half hour dramas were Dragnet, The Adventures of Robin Hood, Sgt. Preston of the Yukon and The Adventures of Jim Bowie. Ten years later, in 1966 (when prime time most nights ran from 7:30 p.m. to 11 p.m. Eastern), there were 47 shows of one hour or longer, and 44 half hour shows of which only 8 could be classified as dramas (10 if you countBatman as a drama; I don't). What happened in those ten years?
I don't know. If you were to ask people why the half hour drama vanished, some would probably say that drama needs longer to develop suspense. Others would say that the extra time is need to develop complexity. Still others would say that dramas need larger casts and need more time to develop the relationships between people than situation comedies, where the relationships are usually clearly defined. Some of those arguments have validity, particularly the one about complexity. Still that suggests that the people who made television dramas to fill a half hour time slot were either doing something inferior or something simplistic. If you get a chance to see some of these shows - just as an example, there are several DVD collections of the original Dragnet (of varying quality) on the market - you would discover that producers who understood the form could do a lot with a half hour.