Why do we really need a new edition of the Avesta?

Geldner about Westergaard’s edition
(Prolegomena, i):
I may say at once that he succeeded
marvellously in accomplishing the most
difficult task, an editio princeps of the Avesta.
So admirably did Westergaard work through
the manuscripts known to him, and so model
the text he provided, that without entirely
new material, there would have remained
little or nothing for me to do. A re-reading
of the texts extant in Europe, I found, promised
but little fruit.