The lead bus is much less equipped to skip a stop if it has more passengers, because there's a greater chance of a passenger needing to stop to disembark. In Chicago, you will see a trailing bus skip but it can do so because the driver hasn't gotten and cord-pulls to signal someone getting off.
That depends on how many/how frequent your stops are. Here in the north of the UK, a 30 minute journey on an urban bus could pass 60-80 stops, many of which will see no-one wanting to get on/off
The one that came to mind as I wrote that was the one I take after work. Most people tend to get off at the train station at the last stop so the bus only really stops for pickups, other than occasionally. The bus goes through an area mostly full of offices and industrial type buildings until it reaches the train station. There's not much inbetween but the same thing tends to happen. Even on other routes here though, busses tend to do the same thing when they're bunched.
