Will you be the one to teach boomer-age payroll accountants to create SQL tables for their calculations? I can give you a phone number to offer your consulting services :)

Of course a custom website backed by a properly schema'd SQL database would be better, but that takes money, time and someone needs to keep it updated.

People use Excel because it's on everyone's computer by default, they have full permissions to do anything with it without needing IT approval and it's surprisingly powerful when you get into it.

And if a client happens to have a really weird non-standard requirement for how their payroll is done, any accountant can easily create a custom Excel sheet just for them - instead of waiting 6 months for an external consultant company to provide them with a custom tool that does 80% what they need.

I understand why people still use Excel, but then, it's to be expected that there will be errors. And that's fine, some errors can be tolerated if the saving for using cheap tools with a cheap workforce is big enough.

But if you want reliability, just don't use Excel because making it bulletproof is pricier than just using SQL for reporting and analysis.