This really shouldn't come as a surprise to anyone who has had dealings with materia in the past. For every major piece of gear, the primary stat materia (strength, vitality, mind etc) is at its maximum value by default. In fact, the only exception to this is some NQ gear, where you can meld main stat materia only up to the value of the HQ gear.
Combine this with the fact that main-stat materia can no longer be used in forbidden melds and it's basically worthless these days.