Why is the food different at two places of the same name?

This is silly and I'm sure there is a good reason for it, but WHY can I eat an awesome meal at one place like Mickey-D's, then drive a hundred miles to another Mickey-D's and the food is terrible! I have found this to be true with a lot of chain stores and I don't get it. I understand that the quality of help may differ from place to place, but all the stores get the same food shipped to them and any monkey can nuke it and put it on a bun. WHY then does it taste different at different stores? Maybe there's a food service expert out there who can school me on this.

2 main reasons.
1st reason: Quality of staff. If the staff aren't as strong in a certain restaurant it will show in the food quality.
2nd reason: Quality of ingredients. Different areas recieve produce from different suppliers and sources. This means that the freshness and quality of the product may well vary depending on where you are e.g fish and chips are going to be nicest close to the sea.

Hope that clears things up a bit.