If you want the default value to be displayed for fields that don’t have a value set then you need to build a filter to do the work and ACF provides a hook for this https://www.advancedcustomfields.com/resources/acf-load_value/
Also, I believe that if you use the field key to get the value in your template that ACF will automatically show the default value…. but I’m not 100% certain of this. It’s been a while since I looked that part of the ACF code.
