The benefit comes from better nodes being shown first. Did anybody claim the ordering was perfect? Of course not. Don't be silly.

Ever heard a joke about "I found it, but it was in the last place that i looked"? Most people, when they find what they are looking for, they stop looking. You, however, feel the need to worry that, if you stop looking, you might miss an even better version of what you are looking for. That is completely reasonable, but it most certainly isn't true for everybody reading an internet forum.

However, even if one goes on to read all of the nodes, having found a useful answer in one of the first nodes, one can more quickly skip nodes that clearly don't provide a better answer.

Experienced users have more tools for being able to discern the quality of replies, even for seeing the reputation of some or all of the replies. Anonymous and new visitors benefit the most from having the relative reputations of the nodes be represented.

The site even benefits from new visitors being much more likely to see useful replies before seeing clearly unhelpful or even obnoxious replies. I suspect the new visitors also find that to be beneficial. And I think that is the case even when they go on to read all of the unhelpful replies (and I also think they are less likely to bother reading all of the unhelpful replies all of the way through if they've previously read one or more helpful replies).

Perhaps you've seen people on the internet write "tl;dr"? That seems to be pretty common. Just because you refuse to resort to that, don't blind yourself to the rather obvious fact of its existence. "Stopping at 1 many times wouldn't have provided me with the very best of the answers" doesn't even come close to refuting "Sorting answers by an imperfect measure of quality provides some benefit" even just in considering somebody stopping before reading all of the replies.

I actually feel a bit silly trying to explain such. But you asked. I hope that was useful.