So, as an example of the way conf.d is supposed to be used, I've provided

a conf.d entry for dropbear that overrides the provided initsctipt.
Just a simple change in “where do we want to listen”, but impossible
to do otherwise without changing the initscript directly as dropbear
does not support any external config files.
So there you have it, the feature now has a purpose.

conf.d/dhcpcd.sh

@@ -1 +0,0 @@
-service_args='-C resolv.conf'

conf.d/dropbear.sh

@@ -2,5 +2,4 @@
 
 cfg_listen_port='2234'
 
-service_pidfile="/run/dropbear.pid"
-service_args="-R -w -P ${service_pidfile} -p ${cfg_listen_port}"
+service_args="-R -w -F -p ${cfg_listen_port}"

init.d/dhcpcd

@@ -3,4 +3,4 @@
 
 service_respawn=true
 service_command='/usr/sbin/dhcpcd'
-service_args='-B -C resolv.conf'
+service_args='-B'

init.d/dropbear

@@ -2,3 +2,4 @@
 
 service_respawn=true
 service_command='/bin/dropbear'
+service_args="-R -w -F"