The manners are different when I'm in the car. On the bike, the attitude is watchful and any courtesy is mainly to get the cars out of the way, or let them get themselves out of the way. In the car, traffic has many more delicate negotiations. So many small bubbles conducting so many small social transactions at stop-start speeds.
The two-lane-into-one-merge throws up questions of position: if one is on the left, one is essentially requesting space to merge. It doesn't do to push, but equally it's not good form to halt in fear of advancing one's case. If one is on the right, the rituals are just as nuanced. One ought to accede to the polite edging ahead of the neighbouring car, and perhaps the one in front if someone should have refused it entry. But three cars? Only inattention or a pathological desire to draw attention to oneself as a helpful person could see three cars creep in ahead.