Newer MacOS versions use zsh as the default shell for both Terminal and iTerm2. Run echo $SHELL to confirm if this is the case for you.
Zsh looks for a .zshrc file upon shell startup, so to continue using zsh while sourcing the contents of your bash profile, you can run the following:
echo "source ~/.bash_profile" >> ~/.zshrc
Open a new terminal window for the changes to take effect.