Point from Usta is sound, it's their own fault but it's a problem that is shared by the other users. Similar to the discussion about telling players about the non-sync'd traffic lights. From my experience alot of rage in towns is from players just not knowing that traffic lights are currently not synced between players, yet when someone suggested including a reminder in the chat window on the odd occasion about that fact, someone said 'Good players know about it, if you don't then it's your own fault'.
By not defaulting the winter mod will mean players won't accidentially have it enabled, which means less people are likely to run it (it doesn't add to the game for other players) which means more people will be able to see the road easier, which means they will hopefully control their trucks better, which means they won't run into you as much.
I don't see the negative there.