I don't like to go food shopping often, so what I end up doing is buying more than I need. I'm anticipating my future needs - short term for meat and vegetables, mid-to-long term for everything else.
So when I buy, I'm rarely thinking of a specific dish, but what kinds of foods I may want in the future. This has two apparent consequences. First, I end up getting things that go bad before they're used. Second, I'm susceptible to the specials and whims of possibility.
Any food I don't end up using is a waste of money. I'm paying for the potential it provides rather than the reality of consumption. And anything that goes into a packed fridge or pantry is out of sight (i.e. out of mind) so it can easily be lost. While I always have food around - which may be of psychological comfort - I'm paying for things I don't use.
There is a way of solving this: buy ingredients on a needs basis rather than an anticipatory one.
What this requires, however, is a change of mindset. That when I shop, I buy based on an actual need rather than an anticipated one. So each time I buy less, but make more trips to the shop. This way I know what I'll buy will be consumed, and that my freezer and pantry won't be full of spontaneous anticipated purchases.
In software design, the Big Requirements Up Front approach is similar to trying to shop in anticipation of what one might need in the future. Like with shopping, what sounds like a good idea at the point of sale won't necessarily translate into what's needed now, or even useful in the future.
The agile approach is for the business to value and prioritise what is needed, not what might be nice to have at some stage. A pantry full of uneaten food would rightly be considered a waste, just as software with unused features ought to be considered a waste.
And like shopping, recognising the problem of waste isn't enough without that change of mindset. The process of 'going agile' is not about following scrum (or any other process) to better outcomes, but embracing a mindset that makes the process effective. It's the shift from "I want this someday" through "I'll better plan to use what I buy" to "I'll buy what I need when I need it."