It's not entirely true that attuning purple IOs is worthless. When purple IOs are attuned you get the full benefit of the set bonuses every level. If your only goals are PVP. And end game content then attuned purple sets are a bad idea. But if you spend a lot of time exemplaring with lower-level Friends or supergroup members it can still be worthwhile.
It depends entirely on what you do with your time.
Attuned Purple Sets???
in Brute
Posted
My understanding, and personal use of both attuned and non-attuned purple sets is the same as shown here: https://cityofheroes.fandom.com/wiki/Very_Rare_IO_Sets
Their set bonuses are available at all levels even when exemplaring to a level where the power the set is placed into is unavailable, unlike other sets.