Nepali Hindu scarify animals to goddesses and gods

I respect all religions and cultures but I critic on those religious Dogmatic thinking and superstitious belief imposed to others. 

It is really surprising to me to know that WHY Indian Hindu don't sacrifice animals during the Hindu festival Dashai but Nepalese Hindu do. This always surprise me because across the globe Muslim and Christian celebrate their festival in the same way and have similarity because their holy books are the same. BUT Nepal and Hindu celebrates their feasts and festivals such as Dashain, Teej, Deepawali, etc in very different says. Interestingly, Hindu they worship 33 corer gods and goddesses, however, Christian they just pray and worship Jesus likewise Muslim has Allah and Buddhist has Buddha. 

The oldest holy scriptures of Hindu is Ved and in Ved nothing has mentioned about animals scarifying thus I wonder Why Nepalese Hindu sacrifice animals in the name of Goddess (Durga/Kali,Bhagawati, etc) in the Hindu religion there nothing mentioned to sacrifice animals!!! 

WHY they don't follow pure Hinduism instead promote their superstitious beliefs and traditions??? 

Vedic God demands no sacrifice of animals, instead declaring it a greatest sin He saves dumb animals (Atharva Veda10/1/29). 

The basic principle is “Live and let live‘,as such there is no question of human sacrifice for elevation of his devotee (such as his first born babies, his sons or his only daughter). Instead, Vedas preach non-violence (Atharva Veda1/31/4, 1/16/4). 

Vedic culture can not think of cannibalism, the entire Vedic philosophy revolves round purity of mind (Rig Veda10/20/1, Yajur Veda 34/1). 

Vedas preach “purity of speech‘ and on ‗sweetness of tongue‘ (AtharvaVeda `1/34/2) and therefore use of the words viz. "dogs‘ for men or "bastard‘ fornon-believers is seen no where in Vedas.