Seems to me the connection between planets and civilisations  of the original Drake equation is dated. Agreed a "larval" civilisation might normally arise on a planet but once a civilisation conquers the limitations of its own bodies planets are no longer needed, entities could live much longer and the growth and spread of entities could be exponential. My feeling (nothing more) is that there are probably PLENTY of civilisations out there but that we are isolatedfrom detecting them because were are still dangerously primitive. If and when that is no longer the case, only then will we be contacted.