http://www.metacritic.com/games/platforms/pc/bigrigsovertheroadracing It's just so lol... Read the reviews. Being that bad is really an achievement.
It has nearly 3 times the points. It's not even close. There are other games that rank much nearer to BROTRR.
Your point? STEAM is a digital distribution platform. If someone wants their game published, I doubt STEAM is going to say no, it's money, and profits. The quality of the game means nothing to them unless it comes out of Valve.
http://www.mobygames.com/stats/all_time_worst EDIT: That stalin game can't be bad.. I mean: http://www.mobygames.com/game/windows/stalin-vs-martians/screenshots/gameShotId,366895/