Are those who simply work, mind their own affairs and forgo social functions perceived negatively at work?

It depends. If the social function is on the clock, then typically yes. Most people I know don't fraternize outside of the office. But if we have a team lunch or team event somewhere it's generally expected that people try to attend. If there is critical work to be done it's generally acceptable to skip. But if no deadlines and always skipping it isn't viewed well.