Please read about Physical Levels and Removing them.

[Reika]

Lol, sales of lower level equipment have stagnated because there aren't enough people in need of the gear, not because you can equip a higher level item. You can equip it, it doesn't work as well and degrades faster, if you're so hell bent on them only wearing level appropriate stuff make it completely useless unless you're ~10 levels under it.

That is assuming you already have all your classes at Rank 50. If you had the money for high gear for your lower rank class, Given that that gear favors that class, would you bother looking at the lower rank gear, knowing that the stats would only be like 1 or 2 points lower?