The upside is that covert ships can much more easily travel around, that covert cynos are very hard to catch (unlike industrial cynos) and that any time hostiles show up in too great numbers the entire mining fleet can cloak up and wait or move elsewhere, unlike barges in hostile space.
Right that doesn’t matter if you can’t actually make any isk. Also, remember regular mining fleets just all immediately conduit to either another anom or onto a friendly structure. So you’re no safer than mining with a rorq.
Adding a compression ship let’s it be competitive with hs mining not with null mining.