The Sages asked Rabban Gamliel, "According to your opinion that the prayer leader fulfills everyone's obligation, why do people first pray silently at all?" He answers, "To give them something to do while the prayer leader reviews what he is going to say." He then asked in return, "And according to you, why does the prayer leader go down next to the ark and repeat the prayer?" The Sages told him, "For the benefit of the unlearned." He concluded, "Just as the prayer leader's prayer works for the unlearned, so it works for everyone else!"
Some say Rabban Gamliel exempted even those far away in the fields and could not attend the services. Others say that just the opposite, he exempted only them because the circumstances beyond their control stopped them from praying, but those who are in the city and attend services should say the prayers. Today, of course, there are printed prayer books, and everyone is obligated to pray using these.
Art: The Daily Prayers by Leopold Pilichowski