this could just as well be an executable that is started to handle that event? Indeed, that's what FreeBSD does, with resolvconf(8). The reason this is a daem

this could just as well be an executable that is started to handle that event? Indeed, that's what FreeBSD does, with resolvconf(8). The reason this is a daemon is ... because a process started from dhclient/slaacd/unwind couldn't directly write to /etc/resolv.conf? I would say couldn't or shouldn't: resolvconf manages resolv.conf(5) files from multiple sources, such as DHCP and VPN clients. Traditionally, the host runs just one client and that updates /etc/resolv.conf. More modern systems frequently have wired and wireless interfaces and there is no guarantee both are on the same network. With the advent of VPN and other types of networking daemons, many things now contend for the contents of /etc/resolv.conf. FreeBSD's resolvconf comes with a configuration file which tells it how to combine instructions from multiple sources.