'I love you like salt', she said, and the king, her father, was so spurned that he rejected her in favour of more flattering praise.
But as we all know, the daughter was professing her essential relationship with her dad - without him, all else would be ordinary. He made her life have substance and meaning. Thus, he was essential to her.
That's the way it is, too, with bread and salt. Without salt, bread has no meaning.
I don't hold too much truck with those who advocate 'salt free' bread - you can make bread even with tiny amounts of salt - so small as to be negligable, and yet it still has a profound effect. Salt is a bit like religion, or 'spirit', or micronutrients. A little is almost always better than none at all, and definitely always better than too much!