It's probably one of those things that might seem more obvious in simple cases, but might surprise folks in more complex cases.
For example, a simple case: Say you go on vacation for a few weeks with a certain amount of cash to spend. Upon arriving at your destination, you immediately purchase some indulgence, and, hey, you're feeling better! Why not immediately keep spending as much as possible to maximize?
For example, a complex case: Say you're leading a country. You set up policies that, after a few years, seem to have led to a higher GDP than was previously expected. Does that suggest that the policies are leading to a better future?
In the simple cases, like the vacation-example above, it's easy enough to understand the scenario and what's going on. And we can imagine that, hey, immediately spending all of the cash might lead to poor consequences for the rest of the vacation, even if they display some quick-satisfaction at first.
But in more complex cases, like with a country's policies leading to a higher GDP, stuff can get trickier. We might say that it's the lack of a top-level model: unlike in the vacation scenario, where we were easily able to predict that there'd be a lack of money later in the vacation, it might be harder to say what else might be going on besides the GDP going up. And all other things held equal, presumably a higher GDP would be better than a lower GDP, and therefore all evidence points toward the policies being a good idea, right?