Soap suds - hidden health benefits?

There is an alarming habit I have noticed and it takes place in millions of kitchens in the UK ( I am certain) including Office Kitchens where I first noticed this habit. And this is it: After (most) people here wash their cups, plates and cutlery, THEY DON'T RINSE THEM!!! Is there something I am missing here or are dried soap suds healthy? As a result, I rarely say 'Yes' when a tea round is offered as I am never sure if half of it is made up of dirty soap suds. Ugh, it doesn't bear thinking about.