Benefits of Transfer and Retransfer Bids
Lets go back few decades when one of the legends of bridge ( Oswald Jacoby ) and his son James Jacoby , another legend of his time introduced Transfers over 1NT openings. It spread like fire , just like Stayman , ( to find 4-4 Major FIT ) and Blackwood conventions ( to find the number of Aces) did. We have come a long way since then . Today we see many variations of transfers in many situations , even over other openings , over take out doubles , retransfers in some situations , transfer overcalls over NT /over Strong Club / over MULTI openings etc. In fact many partnerships world over are playing transfer responses over natural 1C opening which may be 2+ cards.
Biggest advantage of using the transfer bids is that the person gets ONE more chance to BID ON or not to BID ON later . May want to make a game try by bidding second suit or NT or invite in the bid suit.
Without playing TRANSFERS — an easy and glaring example of its pitfalls is when responder DOES have a 5-card Major and invitational values . Responder could bid a NATURAL 2H/2S with weak hand OR bid 3H/3S as forcing . There was no IN BETWEEN bid. Today you can transfer and invite or show second suit to INVITE or to FORCE.