I think it depends a bit on circumstance, but I think I'd start with "way too much software binds to 0.0.0.0 by default", "way too much software lacks decent au

I think it depends a bit on circumstance, but I think I'd start with "way too much software binds to 0.0.0.0 by default", "way too much software lacks decent authn/z out of the box, possibly has no authn/z out of the box", and "developers are too lazy to change the defaults". So it ends up on the network, unprotected.