Why Hindus prefer Eastern direction for offering prayers?

 

Rig Veda is the oldest spiritual treatise on the Earth.

It says rishis used to turn towards East and offer prayers. Hence, this tradition might have been followed by subsequent generations.

----- 

Rig Veda 3.1.2

प्राञ्चं यज्ञं चकृम वर्धतां गीः समिद्भिरग्निं नमसा दुवस्यन् । दिवः शशासुर्विदथा कवीनां गृत्साय चित्तवसे गातुमीषुः ॥
prāñcaṃ yajñaṃ cakṛma vardhatāṃ gīḥ samidbhir agniṃ namasā duvasyan | divaḥ śaśāsur vidathā kavīnāṃ gṛtsāya cit tavase gātum īṣuḥ ||

English translation:

“We have made the sacrifice turned to the east . Let our song become strong.” (So saying) they befriend Agni with kindling wood and with reverence. From heaven they have directed the ritual distributions of the sages. They have sought the way for (Agni), even for the clever and mighty one.