Mending isn't just about clothes, something I already had to point to you. It's not just "superglue" which you have also called it.
It fixes *any* break or tear in *any* object that is under a foot.
Clothes? Sure.
Sword broken? Mended.
Armor got holes in it? Mended.
Arrows broken? Mended.
So when we discuss extending the lifetime of useable objects, what we are really discussing is that objects that would have to be discarded because they are broken, wouldn't have to be. Or objects that would have to be broken down to component parts and re-used.
And think of the difference in time. Again, if you bothered looking at the amount of time pre-industrial societies, especially the domestics (women, daughters, domestics help) in those societies had to spend on repair, you wouldn't think this was a small thing. But not just them, because it's not just clothes. As I already wrote, but you have continually ignored, this would apply to itinerant tinkerers, or smithies, or a lot of other areas as well. And that's just one cantrip.
Finally, I don't assume anything, other than assuming I am playing a game. I do find your "logical conclusions" about aTTRPG to be ahistorical.
Of course my conclusions are a-historical. We aren't talking about the historical world, we're talking about one where magic exists.
As far as the rest, it's a matter of scale. I've repaired clothes many times. Sewing a tear that mending could fix only takes a few minutes. What gets time consuming is washing clothes by hand, hauling water, tending the fire, making soap, weeding the garden, weaving a new piece of cloth because that shirt is wearing so thin you can see through it.
It would also save time repairing that one broken link of a chain, but it doesn't save any time at all when creating a new set of chain armor and you have to weld (or braze or link) hundreds of links.
Correct me if I'm wrong, but basically what you are pushing is that magic should never affect society at large.
That makes no sense to me. Magic is part of the fabric of the world in most fantasy campaigns. Ignoring it's impact is like ignoring the impact of glass in the real world because it's not convenient to think about.
There can be a world influenced by magic without that world going to the extreme of the magic steam-punk world of Ebberon.
To each his own, but I'm done with this conversation if all you're going to do is tell me that "I haven't thought about it" because I come to a different conclusion.