Hilariously they're never found a pair of shoes, only singles. So that's why they think they were thrown away as rubbish, because one shoe broke so they threw it in the ditch. In the museum on site there's a fantastic "wall of shoes" on display where you can see the amazing leatherwork from 2000 years ago <https://www.thehistoryblog.com/archives/37305>.
How could one afford to throw away a perfectly good non-matching shoe?
when shoes are hand made it makes sense to not make them only in pairs if only one shoe is needed
From that first link: “These two little treasures were part of the hoard of over 400 shoes excavated in 2016. One would probably think that we have lots of pairs of shoes however, we only have a few. But this pair was easier to identify as they were small and have a less usual construction style as they do not have a seam that stitches them up over the toe and they were also found close together.”
Also, looking at those shoes, many of them don’t look beyond repair to me. Quite a few look like they’d need only minor repairs.