I don't budget at all, and hence I don't allocate spending money. My reason for not budgeting is because I'm on such a low income; if I put it all down on paper it would probably really depress/stress me.
Some weeks I have not a single dollar spare (including unpaid bills). Some weeks I have some spare dollars, so if I need/want to buy whatever I will do it then. Or, most often, I actually buy whatever I need/want whenever I want, but then it just means that some bills wait until the following week/s.
It doesn't sound overly sensible, not having a budget, but I find it maintains my psychological wellbeing quite well.