Late Roman belt

[Statius]

I use mine for a purse, a knife and sometime smaller stuff. .

Exactly, all stuff that you might want on your person when you're in camp or in town, not when you're on a battlefield.

Whilst I see the logic in your argument couldn't you also postulate that in a possession poor society you're not going to leave your valuable goods such as a knife, coinage etc behind in your baggage but actually want it with you.

What happens if the battle goes badly and you have to beat a hasty retreat or are separated from your baggage train or camp, you've lost all those vital bits and pieces which would be useful e.g. tinder box, coinage and other trinkets and personal valuables. Hence doesn't a belt seem the easiest way to carry them?