I've always thought that tax enforcement pays for itself and then some. Obviously, the government has many budgetary needs. What happened in the United States 20 years ago or so is the IRS became a punching bag politically and took some unfair criticism. And the IRS retrenched its enforcement activity, and that encouraged people to cheat. There are some people who believe that the mass-marketed tax shelters of the late nineties and so forth were a result of a perception that the IRS didn't have any enforcement mechanisms and was not going to be aggressive.
Tax enforcement is a pendulum, and when it swings toward more activity, I believe it promotes more compliance.