The reason is that when you’re an user, you just want something that works. So you can probably become angry, itched, nervous.
And as in real world, you just want to escape the wrong situation, otherwise you’re going to do a stupid thing (fight with the bouncer, break a glass, launch a pineapple on a car…) or start screaming.
These original Error 404 pages have a fantastic purpose: they talk with the unsatisfied user, and make him feel that beyond a webpage, there are just human beings (yes, even @ Google!).
Humour, apologies, every brand has its own tactics. No one is blind, but in a sense, these creatives make you lose less value than without them.
Here’s a little selection: