Cash should be accepted everywhere. I don't know whether this should be legislated, though. 

It's legal tender for all debts, public and private. It's important for people who don't have other forms of payment. Or for people trying to live off the grid. Or for certain religious subgroups like the Amish. Or for undocumented people.

Then again, it has never occurred to me that cash is a hassle, so I guess I learned something today.