/etc/profile not sourced for `sudo su`

Question

I have PATH=foo set in /etc/profile

According to /etc/password the root and myaccount users have /bin/bash as the login shell.

When I log in as myaccount, the PATH has been set correctly from /etc/profile. If I then sudo su, PATH does not include the value set in /etc/profile.

If I sudo su - instead then /etc/profile is sourced. I know it is good practice to do this anyway but I don't see why it's necessary in order to source /etc/profile.

Why does sudo su clobber PATH, disregarding /etc/profile and how to I make it not?

Answer 1

sudo su is an abomination that should be cursed unto the ends of the earth.

Having got that out of the way, you'll be asking what you should do instead.

# sudo asks for *your* password and must be configured via /etc/sudoers
sudo -s             # Shell for superuser
sudo -i             # Login shell for superuser
sudo -u jimmy -s    # Shell for user "jimmy"
sudo -u jimmy -i    # Login shell for user "jimmy"

# su asks for the root password and usually requires no configuration
su                  # Shell for superuser
su -                # Login shell for superuser
su jimmy            # Shell for "jimmy"
su - jimmy          # Login shell for "jimmy"

Only login shells source /etc/profile.