Pro: More exciting.
There’s just something about a bunch of cars bunched together going over 100 miles per hour that gets the heart beating at a rapid pace. Not only that, seeing drivers aggressively fight for spots every single lap is also a lot of fun to watch and creates a level of unpredictability that NASCAR desperately needs right now.
Having the cars all bunched up also opens up the possibility of more accidents, which while that may not be good for the drivers, it helps to create a level of chaos that fans usually only get to see at tracks at Talladega or Datyona. Not that its exclusively a good thing for this to be the case, but it would help attract more eyeballs to the sport to see cars flirting with disaster every lap.