Good question OP and, for a lot of people, a big part of the answer as to why some people seem to have money, and others don't. Leaving aside people who can't even manage modest basic essentials and those who have more money than they'll ever spend in a lifetime, the biggest part of financial security for the majority is how they manage their money and the difference in what they spend day to day.
Eg if you spend £5 every working day on a want that you could do without, a nice coffee being the classic example, that's £25 a week, £100 a month, over £1k per year, or £10k+ per decade, just on one apparently inconsequential 'it's only a few quid' spend.
Apply the same thinking to other things like other food and drink out of the house, days out, holidays, clothes, beauty treatments, tech etc etc and the difference could be hundreds if not £1k+ pm.
But on needs vs wants, what's right for you depends on your life stage and how much money you have.
The answer would be different if you were a young adult who was either renting or living with parents who was looking to save a house deposit, afford childcare, get out of debt, save into a pension etc vs if you were a 50/60 something who was mortgage free in their forever home with pensions, investments and emergency fund etc sorted.
Even for essentials like food, housing, utilities, car, mobile/entertainment packages there can be a significant 'want' component because the cost can vary so much between survival level and 'we have so much money we can get the nicest version without worrying about the cost' position.
If you're wanting to sense your own situation, MSE and the financial flow chart are a good place to start.
https://www.moneysavingexpert.com/family/stop-spending-budgeting-tool/
https://ukpersonal.finance/flowchart/
I do agree that, if you can, you should include some 'want' in your budget, even if in debt or saving for a house deposit, pension etc, but it's also worth being mindful of a pound spent on X, means that it's not available to spend on Y or Z.