If you have a social media page on FB for your business I think its important to keep it up to date and strategise your plan for the campaign. However, I have not seen any return on the FB pages I have created financially, so I think of the system as being a way of increasing brand awareness and building on customer relations.
Existing of business page is now necessary as you can keep in touch with your targeted customers and let know what's new products or services are about to launch. Further, after Google recent updates social indicators are 'MUST' to get higher rank in SERP.
If you have your business page on social media sites, keep them updating even nobody read it or you won't get followers but at least Google is following you on these social networks and that's important for business.