Yes, as my finance professor used to say, make all of your decisions based on after-tax.

Which is very relevant on a personal level to, say, someone buying a house in the US with a sufficiently large mortgage to itemize deductions is going to be... unhappy if that deduction suddenly gets snatched away.

"Rules" obviously do change but there are good reasons to exercise restraint with respect to established rules that led individuals to make substantial commitments on the basis of that rule.