exactly apache is more set and forget.. not to mention alot of linux distributions include apache by default - sure that helps too
nginx need's tender loving care more often due to lack of htaccess and mod_rewrite support and need to convert to nginx rewrites
If you tally up all system admin related hours used to setup, configure and maintain apache or nginx over a course of 12 months, you'll find nginx consumes way more of your time than apache. More sites in the mix, the higher that nginx system admin/maintenance time gets
I'd say nginx will overtake apache when native .htaccess and mod_rewrite support are added - I hear nginx 2.x has plans for that ?