I think it's a combination of us being 'too small' and also sometimes having drastically different needs. Not only do different SFF layouts need different cable lengths, but different motherboards sometimes have different connector placements.
And having less exact lengths is arguably a lot more problematic in a SFF situation, you don't really want to have to manage excess cable. So I get the impression we probably are a bit "needier" of a consumer base, too, that requires more support. So that might also factor into us not suiting their model/scale well.