Most of the HTTP Servers I know send their application name and version in response http headers as default behaviour. (Nginx, IIS, Apache etc.) Of course we can change the default behaviour but I wonder why they send these information? Does it matter which HTTP Servers we use to the requesters?
The only reason I can think of is to allow analytics services to keep track of which HTTP Servers are widely used by websites but otherwise these information are unnecessary for most of the requests and when an attacker figures out a specific version of a HTTP Server has a bug, he can easily find websites which uses that version and use that information against these websites.