If you were to add a money type of an attribute as one of the columns of a view you are designing, when you try to run the view, the results page will show an error message.
This is because the money type attributes require that the currency always be specified along with the money type attribute. To fix the above error all you need to do is include the currency attribute in the view and it will work just fine.
If you design a new custom Entity in CRM, the moment you add a money type of attribute, it automatically adds an attribute for currency called “transactioncurrencyid”. 
If you forget to add the currency attribute on the form, when you try to provide a value in the money type attribute it will throw an error.
We have had various requests from customers who find the “Currency” attribute unnecessary as they work in a single currency and would like to avoid it. It is possible to remove the currency attribute from the form. But you can hide the currency attribute through scripting.
So in short… Money attributes require Currency attribute to tag along with them for them to function correctly.