WordPress.org

What about if I don't want to set a custom menu label for a particular page?

Just leave the menu label box blank and it will use the default value which is the same as the page header.

The title attributes for my pages have disappeared!

If you don't set a custom value the title attribute will not be displayed. There's no point repeating the same content in the title attribute as what's in the label. That's not really accessible. Set a different, more descriptive value.

But I want the same value for my title attribute as my anchor text

Okay, then set the same value in the box and it will appear :)