Why Bala and Atibala hymns imparted to Sri Rama alone?

From Srimad Ramayana

King Dasharatha sends Sri Rama and Lakshmana along with Sage Vishvamitra as requested by the sage.  On going one and half yojanas distance , SageVishvamitra imparted a group of hymns, BALA and ATI BALA to Sri Rama, on the southern riverbank of Sarayu. (Bala Kanda 22 Sarga 11-20 Slokas)

गृहाण वत्स सलिलम् मा भूत् कालस्य पर्ययः ||
मंत्र ग्रामम् गृहाण त्वम् बलाम् अतिबलाम् तथा |

"Take water, my boy, and like that you receive a group of hymns, bala and ati bala from me, and let no time lapse."

ततो रामो जलम् स्पृष्ट्वा प्रहृष्ट वदनः शुचिः |
प्रति जग्राह ते विद्ये महर्षेर् भावित आत्मनः |

"Then Rama on touching water to purify himself received those teachings from the contemplative soul Vishvamitra with gladness beaming on his face."

He told the greatness of hymns, BALA and ATI BALA as follows:

"On receiving these hymns neither tiredness nor fever, nor disfiguring of personality can effect you, nor the demons can charge you either you are sleeping or unvigilant. As it is none whosoever on earth can equal you in dexterity, Rama, and by reciting these hymns none can equal you in the three worlds.”

“My dear Raghava, if bala atibala hymns are practised, none can equal you in the world by your handsomeness, calibre, erudition, by your discernment, and even in replying or rebutting you.”

“ On receiving these two teachings there will be none similar to you, for bala and atibala are the mothers of all knowledge. Oh, best one among men, Raghava, if you go on reciting bala and atiblala hymns, my dear Rama, there will be no hunger or thirst to you.

"And if these twin teachings are practised an inestimable renown will also accrue, oh, Raghu's legatee, these two hymns that possess brilliance are the daughters of Forefather Brahma, and I intend to impart these hymns to you, as you are the most eligible one, hence take the teachings that are kept safe from the world.”

“Though all of these numerous qualities are undoubtedly available with you, that too in abundance, yet these hymns if ascetically nurtured will yield various results."

Here, Sage Viswamitra says that Bala and Atibala are daughters of Lord Brahma and mothers of all knowledge and as Sri Rama was the only eligible person, he was imparting that Knowledge to him.

Sage Viswamitra said the hymns were kept safe from the World.  Sage Viswamitra, was in the know-how of various missiles and can as well control those demons by himself but intends to get the things done through Sri Rama.

Reasons for doing so might be:

1. A Brahma Gnani should not propose to kill people by himself even they are harmful to society because it is the dharma of people from warrior clan to eliminate unlawful people,
2.  He selected Sri Rama among the warrior clan,
3.  Imparting of Knowledge about Bala and Ati Bala to Sri Rama was done because Sri Rama was the only worthy disciple he had ever found among people from Warrior clan

Sages will be ready to impart knowledge to every body but only the worthy will receive it.