When you do create a HTML email template on salesforce for the team to use you are provided the option to create a ‘text’ version of this HTML template by pushing a button.
When you push the button, salesforce will automatically copy over a text only version of the HTML.
The problem with this is that if you update the HTML version you need to then always remember to manually copy it to a Text version. If though, you always leave the text version blank, salesforce will automatically create this for you each time and your Text version will then never not match the HTML version.
Saves you a few seconds, a button press and your text version will always be up to date.