Source: Lima Duplicate Bridge Club
For the newer player, it might make sense to in a very basic manner explain why you would want to use «transfers» at all. There are a lot of complicated justifications, but a few simple ones might convince the unconvinced as to why to use transfers.
First, transfers make sure that the lead comes into the strong hand. Imagine playing Two Spades and getting a lead into this Dummy:
Whatever side suit the opponents lead, you have a finesse. That might or might not work. But, make this hand, instead, Declarer’s hand. Now, any lead is a FREE FINESSE! This happens a lot when the STRONG HAND declares.
Second, and related, having the strong hand declare means that most of the unknown assets will be hidden from the opponents. If the contract instead is Two Hearts with the sample hand, the opponents will attack spades mercilessly if the hand shown is in Dummy. If Declarer has this hand, the opponents won’t know to attack spades as quickly.
Third, transfers maintain control over the auction, allowing you to think for a moment. If you bid Two Diamonds to show hearts, forcing partner to bid Two Hearts, you know what he will do next and can plan ahead. Without transfers, you need to show your hand all in one bid. Taking time is nice.
Fourth, transfers extend the range of calls. Without transfers, a Two Hearts response showing hearts probably is non-forcing but with «something nice.» To force, you jump to Three Hearts. With transfers, however, you can bid Two Diamonds to show hearts with anything from 0 HCP (what else with seven little hearts and garbage?) up to enough to consider a grand slam. Because you force one bid from partner, you have options later, to pass, to invite, to show another suit, to ask for Aces, or whatever suits you.
In other words, transfers are not just a silly convention. Transfers help you right-side the contract, but they also help your auction by taking the stress away.