Sneaker value scanner: point your camera at a pair, see what it's worth and what your whole collection is worth. Tell me why this fails.

Some background: I've been digging into "scan it, see what it's worth" apps. The ones that scan one specific thing (sports cards, Pokémon cards, antiques, toys) are doing really well right now. Coins already have half a dozen of them. The generic "scan anything and flip it" ones mostly go nowhere. Sneakers look like an obvious gap. Huge collector culture. People already check resale prices way too often. And I couldn't find a single sneaker scanner in the top grossing charts, just release-d