Why Sanskrit never became a common man's language?

Re: Why Sanskrit never became a common man's language?

[quote]
and over time most north Indian languages evolved from Sanskrit.
[/quote]

Are you saying that before 3000 years ago there was almost NO language in Subcontinent beside Sanskrit?
If Sanskrit was no common at that time then why everyone stopped speaking it?
If most languages evolved from Sanskrit then why are there grammars so different from Sanskrit grammar?

Urdu is not an Indo-Aryan language, but a local language, which has words from many languages including Sanskrit