A media planner makes everything easier
All these things amount to a much simpler experience for the advertiser. It means that a significant portion of overall marketing requirements can be outsourced to a team of professionals who can take care of the rigmarole of getting rates and booking space for your campaign, as well as the organisational aspect of the campaign.
This means that you will have more time. How you spend that time is up to you – you can work on the product itself, or on other aspects of your business, or you could simply use the time to sit back, relax and watch the return on your investment.