How do you prove you are 18plus?  So you go into a bell store, for example, and briefly uncover your face for id purpose, doesn't that pretty much mean you've broke the religious tradition already? And, who's going to do the verifying?  If it cannot be a non-related male, then what?  What if there's only men working?  Do you demand the proprietor bring in a female?  

The full face covering is plain segregation.  Personally, I love head scarves, they are stylish, look great.  full face?  No.