Nginx installation

I’m trying to install nginx on my virtualmin server.I wonder that why i should uncheck these features and what are they provide.
Un-check the “Apache website” , “SSL website” and “DAV Login”, “Mailman”, “Protected web directories”, “AWstats reporting” and “Subversion repositories” features.

I’m afraid about security after nginx installation and i also wonder why cant i install virtualmin directly with nginx why virtualmin supports Apache more then nginx …