Finding peers is somewhat slow. When downloading via torrent it takes a while to really ramp up in speed. With a centralized repository you can start downloading basically right away. For many small files the latency is more important than the bandwidth, given that most repositories are not short on bandwitdth.
That seems easy to work around. You could write it in such a way that it would have a live cache of peers ready to go plus also the centralized peers would always be available.
I personally suspect that having centralized repos is a legacy technology from pre-torrent days when also disk wasnt cheap.
It seems you would have essentially unlimited bandwidth.