Some bitches that have never raced, the ones that throw on most likely always had ability. So without racing it or at worst having it broken in you do now know what traits the mum will throw into her mums, in term wont know who to put her to to correct any faults.

Ie if mum was slow out you would find a sire who was fast out.

But without knowing what the mum could do then it makes things harder down the track.
Depends also whether you will have her broken in.