Americans generally talk about income in terms of gross. This is very disorienting for people from cultures where “income” as a solitary noun generally refers to post-tax income, but arguing with culture isn’t likely to be very fruitful.
It is absolutely true that this is rarely useful for making budgeting decisions, because you have to come up with some inaccurate assessment of after tax net, which is especially tricky with simultaneously progressive and regressive income tax regimes like the US system for high earners.
The cultural variation around internalizing taxes is even more obvious for transactional taxes, where most of Europe lists prices inclusive of VAT but the US lists prices before sales tax; the US affection for communicating costs while ignoring tax and then expressing distress when they finally appear is widespread.
It doesn’t sound like we really disagree on much at the object level, here, we’re disagreeing on semantics (and, I suspect, on tone).
Maybe it's common in financial circles? But most people I know balance their books based on their take-home, not gross.