It's not about revenue and never was. It's about control and information mining. You have to account for where you got every penny of your income and where you have spent every penny. You have to report to the government where you live, where you work, how many hours you work, how you get from your residence to your work, the size of your family, any medical procedures you have had, the value of your house and a myriad of other personal information.
The government in turn uses this information to enact policies that are intended to alter your improper behavior.
Revenue is unimportant to them controlling everything you do is their goal