As per the discussion
http://ofbiz.135035.n4.nabble.com/Customer-returns-of-type-store-credit-and-BillingAccount-vs-FinAccount-td189402.html.
Are the developers have planned to remove BillingAccount table, in future.
As of 16 Version, Billing_Account table still used by ofbiz. Currently
when the application creates records in billing_account vs finaccount.