OK I get what you are saying. So what are the practices of pastafarianism? What started out as really a joke is now considered a religion.
1) A specific fundamental set of beliefs
2) And practices
3) Generally agreed upon by a number of persons or sects and/or the body of persons adhering to a particular set of beliefs and practices
Sure, atheist have beliefs... the belief that gods don't exist.
But there are no practices of atheists, and certainly no practices that are generally agreed upon.
All parts of a definition must fit in order to apply a definition.
For instance, definition of chromosome: A threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.
You would argue that any threadlike structure is a chromosome.
Edit : Also, if someone says that they are a non-practising catholic, does that mean they are not religious? Why then do they represent themselves with the catholic church?