I don't think it has so much to do with lack of research; I've just noticed that in movies or TV shows, several different aircraft types may be used for one flight. For example, the film about Eastern Flight 401 - shots were taken of an L1011 and 727, though visually the aircraft are FAR from similar. Also, I've seen shows and movies in which DC-10s and L1011s were switched back and forth, and 727s and 737s as well. Most people can't tell the difference between the interior of one plane and another, and are just as hard-pressed to tell a 727 from an L1011. But visually, who can mistake a t-tail aircraft for one with a low tailplane? Or a widebody for a narrow-body?
I think that for the most part, producers play on the ignorance of the public with how they depict airline crashes, mishaps in the air, and planes in general. And they don't have much to worry about, because people are more interested in the plot of the movie than what is going on with the plane.
All in all, anyone with any small degree of aircraft knowledge can watch a movie or TV show and see a ton of discrepancies. And by far the funniest parody of this was the movie AIRPLANE! in which the producers deliberately used prop engine noise when they showed the 707 in cruise! LOL!