Loads and loads of cards rely on terrible hackneyed jokes, though - many of them weren't even funny in the first place. They've been making cards for the last 20 years or more with a huge picture of Delboy on them, saying "Have a triffic/cushdie birthday!!!" - and presumably people must be buying them.
There are also a lot of cards on display in shops that routinely use (or hint at) swear words and sexist themes - not to mention the fact that probably 75% of all 'humorous' cards rely on offensive ageist tropes, inviting you to laugh at the 'hilarious' idea that your friend who is 43 is akin to an elderly person, and thus naturally hopeless, past it and no use for anything anymore. I once even saw an inflatable zimmer frame in a card and tacky gift shop, so that middle-aged people can have a good old chuckle at the expense of disabled and elderly folk, by reducing their many everyday challenges in life to a cheap joke.
What they urgently need to do to redress this is to immediately repeal the law that makes it mandatory for people to buy any cards that they find objectionable in some way, instead of simply ignoring them and leaving them on the shop rack.