Not sure what 'others' you're referring to here. We draw the line based on what motherboard the case can fit. It's as simple as that. In terms of these being big for mini-ITX, just look at the design compromises of the micro-atx versions of cases this size - the Prodigy and Colossus essentially can't fit a 5.25in drive and hard drives are mounted over the motherboard and CPU. With mini-ITX in this size case you don't have these compromises.