+1 for what Richard says. Moreover, if you know that n is small, and you really want copies of all th permutations, then adding a copy message to your block is really simple. But if the permutationsDo: method made the copy, then it would be useless except for very small values of n.
The comment that Richard quotes is in Pharo too. There is a good reason for the current behaviour, and it is documented.
