As explained here, most NG Firewall boxes are installed in router mode meaning that NAT is being performed on traffic. This means all inbound traffic is blocked regardless of the settings in the Firewall, only explicitly port forwarded traffic goes inside your network. Alternatively, most bridge mode deployments are installed behind a NAT device so the Firewall app (and NG Firewall) will only see traffic that has already explicitly been passed with a port forward on the NAT device. What this means is that the "pass all" default in most scenarios means "block everything inbound but nothing outbound", which is common policy for a lot of organizations. In our opinion most of the Firewall's utility is for controlling outbound traffic, however you are free to add rules controlling inbound, outbound or any other type of traffic you wish.
Have more questions? Submit a request