Somebody doing that 5 minutes before you got there just made you wait longer. In some states that's illegal. You can't impede traffic just because you feel like it. The lane is open until it's closed.
Everyone is just too damn impatient and inconsiderate. The same people who do that probably don't obey school drop off procedures, they just stop on the main road and let their kids run out into traffic. Rules are for everybody else to follow. Saps. "Oh no, that person might get in front of me! The horror! No! Can't happen".
It's not "cutting" It's "taking turns" Like we were taught in 2nd grade but many people forgot.