The value would be the time and effort you put into them, they have little intrinsic SEO value which people seem to have a hard time accepting now.
The linking idea is a bit redundant as well, you might as well have separate pages on your main site.
An exception might be you have another business address in another area and want that site to be associated with that place, that is worth doing.
What with social media and all the other stuff google wants us to do, part of the trick is knowing where to focus your efforts rather than spreading them thin.