First of all - you don't need to create an account. You can skip the login page and use our free app.
However, when you don't create an account, we don't know who you are. If we don't know who you are, then:
We can't give you access to your Haystack card collection from other devices
We can't backup your contacts, and we won't be able to restore them for you in case you lost the app or your phone