Ask three people in the same company what a good route looks like and you will usually get three different answers. That is the goal problem.
Why it matters
Minimising miles produces uneven days. Balancing days costs miles. Maximising kept promises costs both. None of these is wrong; they are different businesses. A company competing on reliability should not be optimising purely for distance, and one competing on price should not be paying for perfectly balanced finish times.
Unstated, the goal defaults to whatever the tool assumes — usually distance — and the operation spends years arguing with a decision nobody made.
How you notice it slipping
Routing results are judged by different people against different standards. Dispatch optimises for peace, sales for promises, finance for miles. The planner gets blamed by all three.
What to do
The goal also decides what counts as a good result, which is why it has to be set before anyone judges the output. Without it, every route is simultaneously too long, too uneven and too risky, depending on who is looking.
Name the goal and rank the trade-offs out loud, in that order: what must never break, what should be protected, what may give. Write it down. It is a short document and it settles more arguments than any feature.