Non-residency income was taxed during the civil war in an effort to raise funds for the war effort. Later congress passed a law in 1966 enacting IRS code 877, taxing expats for 10 years after they declare they are no longer US citizens.
These things are rooted in different times. Laws should change to reflect the changing circumstances. I'm hard pressed to think of how they might change given the current debt situation the United States has allowed ourselves to get in.
Either we decide to change ourselves, or be subject to the breaking of the system.