Like the convention of naming characters.
You won't find many Schuyler Vanderpools blowin' into a harmonica on death row; no one in need of brain surgery is breakin' down the door to see Dr. Lucky Lipshitz; and I'm sure only the most devoted afficianado would pay money to see a ballet dancer named Bruno McNulty.
There are obvious basic trends in character names. You will never encounter a tough-guy character in a drama with the name "Maurice" or "Adelbert." note
You will never see a computer geek named "Rocco" or "Lefty". "Ethel" is always dowdy, while "Jennifer" is always a bombshell.
Society has stereotypes that go with most names, and television writers play to those stereotypes. Comedy — especially broad or satirical comedy — can play against type with names, and sometimes talented writing can spawn a new stereotype to go with an old name. The rest of the time, though, writers go with what is known or expected, or else they risk having the characters dismissed by the viewers for reasons that they only vaguely understand themselves.
Foreign and outright alien characters have more leeway, but even with them, certain practices have become standardized.
A primary example of gleeful inversion would be Terry Pratchett's Discworld
— you would expect
Death's white horse to have a formidable, dark-sounding name. Instead, it's called Binky
See also Language Tropes
. Compare Title Tropes
Animals, Pets, and Sidekicks