Do PR agencies need to promote themselves

Dear members,

PR agencies promote brands and products of other people. PR helps to create awareness by means of promotional activities. But the question that comes to my mind right now is that do PR agencies need to promote themselves. I am asking this because I have received requests from some agencies (may be new into the business) asking for Google advertisements, Facebook ads and ads in other media which I actually found a bit surprising. So my question is, is there any necessity for PR agencies to promote themselves either by advertising or marketing? in case if there is a necessity should they advertise or do marketing for the same ? 
Rajat B

The wise man speaks because he has something to say, the fool because he has to say something