one important thing goals do

If a leader doesn’t clarify what success looks like and get the team to agree, people's assumptions about what constitutes success are often too low. They formulate their assumptions based on their assessment of their own capacity. In my experience, that assessment is always an underestimate. They assume too little of themselves.

A goal is valuable because it prompts you to surprise yourself. You can do better and do more than you might have thought if you were being strictly actuarial or historically focused. Put differently: without a good goal that a leader maintains as a focus for the team, people benchmark to themselves… and not the best of themselves. 

I tend to ask: don't you want to know if you’re actually underperforming? Don't you want to know what you're capable of at the individual level? Of course, at the team level, if you've got a bunch of people consistently underperforming their best, you have a resource problem. This is the kind of problem a leader is typically tasked with fixing.

The very presence of a shared goal can prevent all kinds of waste that is really draining for employees. Absent a goal, you’ll see undue time, cash, and energy spent on arguments and workplace politics. A goal can helpfully simplify the life of the organization and channel the energies of your people, so that the same volume of inputs from them (hours, meetings, etc) generates much better outputs. Outputs they might not have thought they were capable of.
-ben