I think I've finally worked out why there's such a difference in attitudes towards budgets between the public and private sectors.
Imagine I need to ask for £1m for a project budget, here's how I now know the conversations would go:
Private sector: To get a budget like this approved I'll need to get people at the very highest levels of the company to sign it off. In many of the professional services companies I've worked for this will be people who are paid based on the profits the company makes. This makes for some very subjective and emotive decisions. For example, a company that makes £100m profit and has 100 Partners will share that profit at £1m each, if I then ask them for £1m, I'm asking them to give me £10,000 straight out of each and every one of their personal pay-packets. It forces me to make a solid business case for it and sometimes show why it won't return money but will make their jobs easier or meet regulatory needs. It also forces me to take the long-view on payback and justification. I get overall project budgets that I've justified over the project and won't have to fight for that money again.
Public sector: To get a budget like this approved, I'll either have to try to get a slice of a bigger budget that someone guessed might need to be spent and now needs to spend or lose, or I'll have to try to justify why the highheidyins should go ask the evenhigherheidyins for a slice of their guessed budget. I get arbitrary spend dates based on when the higher-level budget has to be spent and pressured to make unnecessary spends to help meet that need, I also get arbitrary demands for re-justification and can have my budget whipped away at any time on the whim of someone who wants to spend it on something else.
The difference is that in the former, I need to ask the money's genuine owner to sacrifice their personal pay-packets, in the latter the budget holder has no consequences if he spends what he says he's going to spend regardless of how it's spent. It's all about accountability for money and making it somehow real money for the public sector rather than figures on a spreadsheet. I think I know how I'd fix it and have a few good ideas that I need to bottom out before I start proposing them.