Category budgeting suits variable, controllable spending
If your spending is spread across many areas and you want to change a specific habit, per-category limits give you the resolution to do it. You can see that dining is the problem and groceries are not, and act on exactly that.
The cost is maintenance. Ten categories mean ten numbers to review, and a month where one category absorbs another's spending looks like two failures rather than one reallocation.
A flexible target suits stable, committed spending
If most of your outgoings are fixed — rent or mortgage, utilities, insurance, loan payments — then budgeting them is theatre. The amount is the amount. What is genuinely under your control is the discretionary remainder.
Splitting expenses into fixed costs, non-monthly costs and flexible spending, and then managing one number for the flexible part, reduces the whole exercise to a single question you can answer in ten seconds: how much is left?
Non-monthly costs deserve their own treatment
Annual insurance, quarterly water bills, car servicing and holidays wreck monthly budgets because they are not monthly. Dividing the annual cost by twelve and accumulating it month to month turns a crisis into a withdrawal.
This is the single highest-value change most people can make to a budget that keeps breaking, and it has nothing to do with spending less.