I thought the same thing. This comment on crypto.stackexchange.com[1] shed a bit of light for me:

    Yup, entropy sources may even have a particular bias to bits valued 0 or 1.
    Normally you need at least a whitening technique to get something looking
    like a random number. Feeding that as a seed into a PRNG is certainly
    helping to get the right quality. Be careful not to confuse a source of
    entropy with a secure random number generator.

[1] http://crypto.stackexchange.com/questions/726/what-is-the-us...