Why doesn't a musical phrase end at the end of a measure but usually in the middle of one?

Question

Referring to standard musical notation. Also, why are the pick-up notes to the B section of a song actually in the last measure of the A ending?

Answer 1

I don't know if there is an answer to your first question...my guess is thats where the composer put it...maybe so you can take a breath. Pick up notes are usually in a different measure as the beginning of the phrase they are picking up because...they are pick up notes...I don't know...