I4: Small, cheap to produce, easy to make into a relatively smooth motor
V6: Small, cheap to produce
V8: Well balanced, not too long
V12: Very smooth
Basically, it's all up to packaging constraints until you get to the V12. All of the most common motor configurations these days reflect the fact that dimensions, especially length, need to be small to fit in shrinking engine bays. Also, given that most cars are FWD these days, long engines are highly undesirable.
>>4629985>>4629971Cars that totally represent the average vehicle and answer the OP's question.
