Computers remove the need to have an army people to open envelopes and file all of the tax returns of the many millions of people who aren't getting audited and now file electronically, and electronically process payments or tax refunds, and validate the numbers on each tax return against the 1099s and W2s submitted by employers to make sure they match etc. All of these things used to be done by hand and it should certainly not require anywhere near as much labor to do them electronically.