You would not believe how many times ive had this exact discussionin group rides specially with people i dont know. But of course big egos get in the way of riding safely as people have to ride up your tail to prove they're fast...usually in the straights! Ironically enough, its almost always new and less experience riders who behave this way as experienced riders know better!
Stop trying to prove yourselves by putting others at risk. Give the rider in front some room to breathe. Leave some room for error, gravel, oil, animals running on the street and in case the guy in front of you has to hit the brakes hard or goes down, you dont wanna run him over while going down yourself.