There are many aspects of an engine that seem counter to common sense.
Why use two overhead cams when one will do the job?
Why use eight pistons when one is more efficient?
Why use and inline cylinder configuration vs. flat or rotary?
Why would anyone choose to travel with several gallons of highly toxic combustible petrol/gasoline/diesel within a few feet of themselves?
The earliest combustion engines were much more primitive than today's modern versions, this means that the improvements we've collectively made to the design were non-obvious/counter-intuitive and were generally arrived at through a process of trail-and-error.