Why do so many people think that if you're not a social person than there is something wrong with you?

Today there was an article in the Daily Mail about a woman whose husband doesn't like any kind of social gatherings and would much rather stay at home with a book than go to parties. I don't see anything wrong with that, in fact I'm like that, but obviously other people don't see it that way since there were numerous comments to the article suggesting that this man must surely have Aspergers syndrome or mild autism since he doesn't like being social.
Then there are the comments that this man must be extremely selfish for often refusing to go to parties with his wife, but no one seems to think that his wife who constantly tries to change her husband and force him to go to things that she very well knows he will not enjoy, is selfish.

Why is it so hard for some people to accept that someone can be really introverted, and not like being social without there being anything wrong with them? Preferring a book to other people doesn't mean that one is a freak or that there is something wrong with one. To suggest that one has to have some sort of syndrome or illness if one doesn't enjoy social gatherings, is just extremely insulting.

The kind of people I dislike the most are those that cannot tolerate that someone is different from them.