The answer is simple really. The car is one unit, the bikes (in this scenario) are two units, they don't have to be considerate, but they have the option to do so.

I'll give an equivalent example. Where I live we have a class of vehicles referred to as "moped cars", same form factor as cars, but speed restricted to either 30 or 45 km/h. Usually they're used by teens to get arouns in rural areas with poor public transit options, so they'll often be trundling along on 70-90km/h roads at slow speed.

This can quickly lead to queues building up behind them during high traffic hours in areas with few passing opportunities. Quite often, when this happens, they'll pull off to the side for a few seconds at an opportune spot to let other, faster vehicles, pass by. They don't have to do this, but it is considerate.

As for the second half of your comment, each method of transportation has its niche and purpose. The best system is one that utilizes the strengths of each to complement the others. Attempting to apply a monolithic solution everywhere will generally lead to frustrations and inefficiencies.

Pedestrian - Trivial distances, any density.

Bike - Trivial -> Short distances, any density.

Cars - Short -> Long distances, low density.

Busses - Short -> Long distances, medium density.

Rail - Short -> Long distances, high density.

High Speed Rail - Medium -> Extreme distances, high density.

Air - Long -> Extreme distances, high density.