If we gave a cognitive test to most clients who make quarterly payments we would find two types:
1) Those who could avoid making quarterly payments by having enough tax withheld from pensions or Social Security. (I discourage Social Security withholding because it's too difficult to stop or change, but for some people it's an acceptable alternative.)
2) Those who are self-employed or otherwise have income not subject to withholding. By July 15, we knew how much they had made the first half of the year, so that provided some basis for how much to pay on that day. But if they tell me that they want to assume the same income and deductions for the rest of the year, it just makes me wonder about their planet of origin. If they don't schedule a certain amount for September and January, I won't have to answer questions later about how to change the figure.
Quarterly payments used to be a profit center for certain practitioners. Some of them even required quarterly visits to update the numbers. This just fed the obsession that some people have with taxes. We should try to steer them away from the quarterly ritual, by urging an easier alternative.