Purple makes a very good point regarding money. People handle it so much without ever thinking about what might be on it and washing their hands before eating.
Anyway to add to the story I have to say that if this bothers people so much then why are you not complaining to management of the shops. I'll give you a story from a couple of years ago. My local Supervalue had a similar stand of deserts and I regularly saw people picking up unpacked stuff, sticking their nose at it and then putting it back, or kids taking little bites. I asked to speak to the manager and was told he wasn't available until the following day. That suited me perfectly as I knew that on the Friday afternoon the place would be full of shoppers doing their weekend shop.
Anyway, I went in, called over the manager and made an almighty scene over the hygiene of the unpacked food and called over random people to ask their opinion, which attracted a crowd. Went back a few days later and they had replaced the table to be much higher out of reach of young kids and all the food was now in either paper or plastic wrapping.
You need to complain in a very public way and ideally in numbers, otherwise nothing will change.