> Someone one a big endian machine, would have to do a lot more legwork to get the thing working. But given that there aren't many of those around, it was deemed an acceptable tradeoff.

Even PowerPC64 has a little-endian mode - PPC64LE.

The machines are switching over because the expensive part is turning out to be software which is already working & the costs associated with migrating it over to a different endian system.