We know that though. Likelihood is a lot of them are the same ones that still find something to moan about in a season like this - otherwise they'd be there supporting the club. So in terms of atmosphere, they don't add much anyway.
Really, transport trouble doesn't come into it. If everyone who is able to get there 15-20 minutes earlier did that, it'd almost certainly be fine for those that genuinely have to leave it to the last minute because of work commitments etc. 15 minutes, that's all. Most people can manage it...