That's more or less the point - I don't think there is any good reason anymore. A modern Linux distribution is not really that different from what Jolla is trying to achieve with Mer - some pieces of software (mobile middleware) might have to be packaged for it but that should be it more or less. The important pieces are on top (mobile UI, mobile applications. etc.) but they are not getting enough attention due to the "guts" eating a lot of time just o keep stuff kinda working.