Budget. Couple. Simplicity.
Each Duo Split account is linked to the Gmail address associated with a Google Account. This email is persisted into Duo Split's cloud storage as well as on the mobile device. It is the only data that is retrieved from a Google account. The rest of the data that is stored comes from the user itself, not a third party service. The Gmail address can possibly be used to contact a user directly by email. In this case, communications are related to Duo Split only and not affiliated marketing.