Script at /etc/init.d does not run at start-up

Script at /etc/init.d does not run at start-up

I wanted to run my Dropbox daemon automatically at start-up. I did it via
terminal, that is, I (1) moved it to /etc/init.d, (2) made it executable,
and (3) ran sudo update-rc.d dropbox.sh defaults. So we have
$ ll /etc/init.d/dropbox.sh
-rwxr-xr-x 1 root root 38 Aug 16 00:18 /etc/init.d/dropbox.sh*
$ cat /etc/init.d/dropbox.sh
#! /bin/sh
~/.dropbox-dist/dropboxd &
$ ll ~/.dropbox-dist/dropboxd
-rwxr-xr-x 1 skrd skrd 258 Jun 6 03:03 /home/chad/.dropbox-dist/dropboxd
However, Dropbox does not run upon start up.
I know that Ubuntu has a GUI for this and I could easily just add the
dropbox script there but I wonder why my terminal commands didn't do it?
Isn't that more standard for Linux machines?