It seems like you either didn't actually read the RFC or read but didn't understand, then made a fuss out of your ignorance.

SRP uses SHA1, but not just that. Here is the relevant part of the RFC [1]:

The host stores user passwords as triplets of the form

        { <username>, <password verifier>, <salt> }

   Password entries are generated as follows:

        <salt> = random()
        x = SHA(<salt> | SHA(<username> | ":" | <raw password>))
        <password verifier> = v = g^x % N*

[1] http://www.ietf.org/rfc/rfc2945.txt