I think I’d have to agree with PT on this one. The hardest part is building up the habit. I’ve learned that in many, many different fields, once you’ve built up the habit, you can feel naked and kind of wrong when you ~don’t~ do it every day. As a beginner, we ~need~ to build up the habit, the muscle memory, and create that need not just to write (which is hopefully already there), but to set aside the time to write. We need to make the habit to learn just how much time we need to set aside and how many words a day will be enough to actually get things done in a timely fashion. We build up the muscle memory within our own psyche by doing this. Once we find the routine and scheduling that we need to accomplish our goals, once that repetition is followed through enough times, our day won’t feel complete until we actually do it. While it could be argued that it’s not that hard to jump off the bandwagon even then, well, check out my first quote in my signature. It applies here too. Far more challenging to get the ball rolling than to hop back on even once you’ve fallen off.
So for authors who already have that habit and muscle memory built in, there’s less need to put focus on word count. The need’s already there. I think a solid point you’re making here, though, is that every individual is different. There are those (such as myself, at least so far), who still need the habit. Who will just keep procrastinanting unless I say I need to get this many words down by this time. I need the structure, and the line that says ‘this is enough, you can stop pulling your hair out by the roots now’. It also gives me that small yay when I’m able to surpass it because I’ve hit my strive, and when I actually ~want~ to say, ‘just ten more minutes, I’m in a good part’. I don’t know if I’ll ever be able to go without it, if I’ll ever ~want~ to go without it. Everyone’s different though, and what’s good for the goose isn’t always good for the gander.