You guys have likely been using them without even knowing it.
The Big Six items are:
Stat boosters (Belts of Strength, Headband of Charisma etc.)
Cloak of Resistance
Ring of Protection
Amulet of Nat. Armor
These items are deemed 'necessary' for survival at higher levels. Some classes don't need all 6 of the items, like Wizards, or some need alternative items, but in general, these are the items almost every character ends up with.
Sorry for the misunderstanding. I/we fall into the "don't care about them" category. They are certainly nice to have and no one will kick them out of bed for eating crackers, but a large number of my past and current players aren't as interested in them as they are other magical devices. They're expected and ordinary in their minds.