That's a really good example you just brought up, because if your goal is to get billion watch hours a day:
1. Why are you doing this? Is it to get more ad revenue?
2. Considering this metric, how do you know that the extra hours you are getting is the kind of traffic that brings ad revenue? Maybe it's children or folks from poor country. Maybe it's actually costing more than it was previously.
3. Maybe you are getting the same people to watch more, but it won't make them pay more. You are just increasing your server costs. And making those people addicted to your platform.
4. Maybe the algorithm that you produce is actively harmful to people by making them take too much screen-time leading to potential regulations from the government.
5. Maybe the content you provide is of really low value, and in the long run will make your audience really low value.
6. Maybe you just pay too much for that extra traffic, so it's not worth it.
Very simple example when doing ads. If my goal is to get 200% more clicks, and I have been so far advertising in US only, I'll just now make the destination to be India instead. I will get tons more clicks, but I will get less payments than before.
> And if it's impossible for something that matters to be represented by a number, what does matter? I'd love to hear examples of what matters in your companies
If you want a number, profit obviously matters, but everything below that, can mostly be intuitive unless it obviously fits some sort of numerical idea. In such case building a great product matters, but it's much more difficult to measure what makes a great product, so you need this intuitive discussion and people who have great intuition for building a good product. Profit will follow performing this strategy.
You should measure, monitor, use data to be informed and analyze results, but you should not have these as primary goals to strive for. You should use this data to improve your intuition.