Ubuntu – Why isn’t .profile sourced when opening a terminal

From your comments on my original answer, it appears that your real question is "Is ~/.profile sourced by GNOME?" The answer is yes. Look in /etc/gdm/Xsession:

# First read /etc/profile and .profile
test -f /etc/profile && . /etc/profile
test -f "$HOME/.profile" && . "$HOME/.profile"
# Second read /etc/xprofile and .xprofile for X specific setup
test -f /etc/xprofile && . /etc/xprofile
test -f "$HOME/.xprofile" && . "$HOME/.xprofile"

Original Answer

From the manpage of bash:

When bash is invoked as an interactive login shell, or as a non-interactive shell with the --login option, it first reads and executes commands from the file /etc/profile, if that file exists. After reading that file, it looks for ~/.bash_profile, ~/.bash_login, and ~/.profile, in that order, and reads and executes commands from the first one that exists and is readable.

So you may have a file called .bash_profile or .bash_login in your home directory. If either of these exists, bash will use it instead of .profile.

Per default, gnome-terminal does not start bash as a login shell (I assume you mean bash started inside a gnome-terminal). That means bash will not read /etc/profile or ~/.profile. As you have correctly observed, bash will read those files if started as a login shell.

The quick fix to your problem is to configure gnome-terminal to start bash as a login shell so it will read /etc/profile. To do that you have to enable "Run Command as a login shell" in the gnome-terminal "Profile Preferences" reachable from the Edit menu.

I do not recommend doing this because it messes up the distinction between ~/.profile and ~/.bashrc. Ideally ~/.profile should do stuff which is required only once, during login, while ~/.bashrc should do stuff which is required everytime bash is started.

There is a question and answer at superuser talking about the difference between bashrc and profile. Read there for more information.

From your problem description it seems that the rvm script needs to be loaded only once, during login. As far as I know Ubuntu has configured the graphical login to read /etc/profile/ and ~/.profile. That means, after logging out and a logging in once, the rvm script should be active. If it still doesn't work, then perhaps the rvm script needs to be loaded for every bash session. If that is the case then bashrc is the more appropriate place for the script.