Humor doesn't always age well.
The style of presenting a gag changes, for one thing. Setups that are fresh and innovative when first presented can seem tired and lethargic when viewed after 40 years of other comics building, tweaking, and distorting that initial joke.
Other things, we're just not comfortable laughing about anymore. Tastes and sensitivities change, and while there are things we'll joke about today that would scandalize previous generations, it doesn't take a lot of digging to find jokes from the past that we'd find outrageous today (say, practically anything Frank Sinatra ever said onstage to Sammy Davis, Jr.).
But sometimes there are other problems, too.
Kathy & I were watching Woody Allen's 1969 film Take the Money and Run, which on the whole holds up really nicely. I'd never seen it before, and it's so light and silly that it just gallops along. Most of the Woody Allen comedies I'd seen were quirky, human-scale things, with the humor coming from character's insecurities and neuroses. This, though, was full of sight-gags and non-sequitur, like when Allen's character's girlfriend "makes him a home-cooked meal" while he's in prison: a hard-boiled egg that she presses through the screen that separates them in the prison visitation room, replicating those wire egg cutters somewhere in the back of a kitchen drawer in ever house.
But there's one moment that used to be funny, and simply wasn't any more. Allen's character (Virgil) is applying for a job at an insurance company, and just lying his way through the job interview, since as a lifelong thief, he doesn't have any job experience. (As an example of how bad his lies are, when he's asked what kind of an office he used to work in, he says "rectangular.") Further along in the interview, he has this exchange with the manager:
INTERVIEWER: Have you ever had any experience in running a high-speed digital electronic computer?At the time--the year I was born--"My aunt has one" was a ridiculous answer. It was the height of absurdity: What the hell would his aunt be doing with a high-speed digital electronic computer?
VIRGIL: (A short pause.) My aunt has one.
Now, of course, there's one in every home. That joke simply doesn't work anymore.
And when I realized that, I laughed so hard I had to pause the TV until I could catch my breath.