Why are Post cremation practices similar in almost every religion?

In general, In every religion, After death the practices they follow are similar, they may burn or bury the body according to their religious belief.

In every religion, Say in Hindutva, There is a belief that lord shiva resides in the graveyard to accompany the souls there, and in Islamic culture, they keep flags, In Christianity, They bury them along with a cross.

The common thing is all about belief, they believe that god accompanies them after death, and they say after death the soul is not lonely, they have the company of supreme energy/god.