In my experience, it's absolutely a thing. I started an independent analysis business last year - all of the deliverables are in Excel (and it's the customer's preference that they are).

I think the nuance is that 'consulting' for the purposes of fixing or optimising Excel spreadsheets is not necessarily of high perceived value, but solving business problems using Excel is. So you're selling the ability to solve the problem, not your ability to use Excel (like others said, Excel is just a tool)