How to run httpd on macOS without Apache
There is a LaunchDaemon service for Apache in /System/Library/LaunchDaemons, org.apache.httpd.plist. You can load it using:

sudo launchctl load -w /System/Library/LaunchDaemons/org.apache.httpd.plist

Obviously you'll need to configure httpd.conf appropriately first.

The -w should set the .plist's Disabled key to false so it will start on boot.

NOTE: load is classified as a legacy sub-command of launchctl but still works in High Sierra. I attempted to start Apache with sudo launchctl enable system/org.apache.httpd but it didn't seem to do anything, possibly because I have no idea how to use enable. :P

DOUBLE NOTE: Apache needs elevated privileges, hence nothing happening when you just ran httpd. sudo httpd will work but again configure it first.