Yes it matters. You have to know the direction of causality.

Consider it in different words. "Tired people are bad for themselves, for process, and for projects." To many, this will read as "hire folks that aren't tired." Worse, it will be "your folks are tired, so they will make things bad for themselves, their processes, and their projects."

At best, you will get people who will see it and victim blame in a way that won't help. "You are jeopardizing our ability to succeed with your tiredness. In addition to your current tasks, I'm assigning you the job of getting less tired." So... odds of increasing wakefulness, slim.

Now, it could turn out that it is something you can fix in this way. I don't know and that is my point.

It does matter. If unhappy developers cause bad software then the solution is to make the developer happy and the software will fix itself. If it's the other way then the process is the one that needs fixing.

Developers can also become unhappy when they are working on products which they think either aren't important or aren't ethical.

For current issues yes, it doesn't matter you just fix it and get the results. If you want to prevent it in the future it helps to know which one causes the other. Then you can focus preventative efforts on the factor that causes the issue.