The biggest businesses in the world can cover all bases. There is not a department that they can’t staff; if they need food they build a catering department, they need PR, they’ve got it covered, there is simply nothing that they cannot afford or staff. But what about you guys? What about your business? For those smaller sized companies that cannot afford to throw money at departments and keep permanent staff for jobs that maybe they don’t need full time.
Outsourcing then becomes an option; or using other companies on a consulting basis. There are specific companies that can help with your PR for specific campaigns, rather than working with you full time when campaigns are on the backburner. For things like website design it might be cheaper to opt for a one time consultancy fee, with the option to call back for any issues, instead of having a full time web department.