點解性交又叫左『做愛』？

我個人認為咁多資料性既野對你問題幫助不大

做愛: 做左就有愛

即係性交完畢後就有愛情了

由英文Make Love直譯過來，性交可通用於所有有性繁殖既動物，做愛通常用於人類．．．

this is just a "better" or more poliet way to talk about sex, cuz love making involves love in the sex... and sometimes "sexual intercourse" (性交) can be too technical and textbook like, and doing it (做) can mean having sex without love which is not as nice to hear as love making, basically they are all the same thing!