I think since epilepsy is such a scary thing to witness, that people's main way of dealing with it is through humour. Not that it justifies it, but it may explain why.

I've never heard of the movie and I'm sure I'll never watch it, but I have come across epilepsy-humour in other films and just through people in general. But I think it's one of those things that you can only be humourous about if you have it.