In Bridge, Why Do People Use "Transfer Bids" Over 1 NT?
A much more important reason is to allow the responder to describe their hand more fully. A 1NT opening bid describes both shape and point count and so it's usually up to responder to then set the contract - the 1NT opener will typically not bid again. However, responder with points for a 2NT raise and a five card major is in a quandary. Bidding 2NT may mean missing a 5-3 major suit fit, but bidding 3M may take them past the safe level of 2NT if opener is minimum. With transfers, responder gets two bites at the cherry. Holding five spades, responder bids 2H. Opener converts to 2S and now responder bids 2NT getting across shape and point count and leaving opener much better placed to set the final contract.