Call Coil Question

Do subroutines started via a true call coil go thru the full  ladder process (read inputs, process logic, write outputs)  before returning to the main ladder? This would be make them useful if you are repeating a process such as a decimal to binary conversion, etc.

If not, then is their value in allowing rungs in the subroutine to be skipped if the call coil is not energized?  That would at least save some processing time .

If neither of the above are true, and the subroutine gets scanned every time in sequence with the main ladder, it seems like there would be nothing to be gained by using a call coil vs just keeping the rungs in the main ladder.