Yes, valid uses and legitimate users still do exist, which is why I don't think it should be removed. Like you say, 99% of the time mass file trading IS illegal file trading, so I think we can let that one slip?
Whilst I cannot speak for others, I myself almost ALWAYS point out the morals of how mIRC/IRC being used for mass file trading when it is a CHAT program is wrong. You make referrals out to be some sort of bad thing...the very reason sticky posts exist is because they answer questions which are answered over and over again - and also, the fact that they are posted by Moderators lets the user know what the helper is telling them is true. So when I say to someone "We do not help with illegal file trading on these Forums" I can back that up with this post
posted by Karen. The legalities of the issue are also mentioned simply to reinforce the fact that mass (sorry, illegal) file trading is not a good thing.