Why did Pakistanis decided to keep Thier pre-islamic sirnames while Muslims in rest of the South Asia didn't?

[SaadH]

Pakistan population is more clan and caste based as well as tribal, whereas Muslims in rest of South Asia are more urbanized and less tribal.

 

[bababho]

Like the current India, the entire sub-continent has strong clan / tribal entity. Their life style, beliefs, culture are deep rooted and heavily influenced by the social structures. It is evident not only in Pakistan but in India, Nepal, BD as well, Muslims, Sikhs, Christans have not left their ancestry event after moving to a different religion.

Dhar became Dar
Bhat became Butt
Wani/ Bajwa/ Choudhary/ Rajput/ Basra/ Sethi/ Malik/ Gill remained Same (both HIndus & Muslims)

Basically Its same people influenced by different books