They are about as much thin content as you can get... most everything is the same other then to make the whois different with stats from one page to the next.... so content wise, they really do not serve that much of a purpose compared to actual content that would be considered higher in quality or value. any links on whois pages are certainly worthless, or bottom of the barrel, or even no value... So why are whois sites still around? any ideas?
Because they are useful. If you wanna know who is behind a certain domain you still use a whois site, don't you? Google tries to give you the most relevant results. If you search for 'whois' you want to be taken to a whois site. Is there more content needed (or useful) than the actual 'whois' data? No, so Google probably consider other factors. Content isn't always king. You can try to beat all the whois sites within the SERPs by adding more content to it (if you think that's underused in all the whois sites). Diversification gives you the ability to choose. Do you profit by providing your own whois site? Probably not (unless you're somehow provide more value than all the others or market them better).
Our "whois website" is here - http://whois.online-domain-tools.com/ And it is doing well. Why? It simply provides what people need. There are many situations when you want to see WHOIS data for a domain. Yes, you can use a console/system application to get the data, but people are somehow more comfortable with in-browser interfaces today than with console line applications. They tend not to leave their browser.
Whois pages are still around because they are useful. Similar to 'Lookup IP address' or 'Is my site down'... etc. To get traffic for these types of 'thin' pages, you need a different strategy to compete with others.