what about the smsf earnings ? they seem to be $0?what if we...

what about the smsf earnings ? they seem to be $0?
what if we assume the external fund earns 3%. But so does the superfund earn 3%
also the external fund has to pay tax.
So Im at a loss to work out how you will earn more money outside of your smsf.??
Logic also says if that was the case everyone would cash out their super! - which they don't. So theres got to be some redeeming features.