We have been running multiple sites, all for over a decade and the authors have degrees that either exactly or closely match the topic areas of the websites. Until two years ago we considered that all articles were written by "our staff". However, we then added author bios with degrees, certifications, years of experience, Google scholar, relevant employment history spanning decades. Within a few months after that these sites received a rankings boost that was surprising.
Now, you ask about "the importance of bios". Adding bios for the sake of adding bios is probably not going to do much for you. Instead, it is the quality of the authors that is important.
If you have authors who have substantive, long-term, quality education, experience, and work history, then that, I believe will do something for you. If your authors have a publication history on important sites, with lots of links and citations for their work from government agencies, academic publications, professional societies - all of this that you can link to, then you have built a gold mine. Very hard to fake, easy for Google to confirm, will attract links like bugs to a Georgia porch light.
It will be really hard to fake a publication history over three or four decades with links from loc.gov and important websites across your discipline and professional registrations on government websites.
