I was trying to buy Ice cream for my kids and I wanted to use my Amex Clear card I just got, but the Lady at the place said they didn't accept Amex, so I took out my MC, and paid it like that, does anyone know why sometimes they don't accept them?? thanks!!!

I use my AMEX Blue for all of my purchases, but I always keep a MC with me for instances like this. Most smaller businesses and mom and pop stores do not except AMEX.

Because it cost businesses money to be able to accept Amex.
My husband restaurant used to accept it but then had to quit because it was costing to much money out of his pocket.

Credit card companies - not the banks that issue them, but Mastercard, Visa, Amex, etc. - charge business a certain percentage of each transaction any time a card is used. Most of the time the business eat the expense because they'd rather have a sale than not. That's how the credit card companies (NOT the banks) make money. Amex happens to charge a high percentage compared to the other cards, and so many businesses do not accept it because most people have cards other than Amex that charge a lower fee to them.