From Apples standpoint yes it's great, I think developers would prefer to hear facts such as about how many users are active on the store, distribution of downloads, median number of downloads per app and revenue. It's like a boss holding a meeting to discuss how great his/her own bonus is this year.
It's more like the boss showing off the stock price. It gets everyone excited because the company is doing 'well.'
The only thing your metrics would do at WWDC would be to cement that unless you're the top app in your category, you're not making money, and Apple knows this. As long as they're super popular though, developers will keep trying.
Also, why would Apple do anything at their event other than make themselves look great.
And honestly developers, individual and companies, are peer pressure driven. As long as others make it a popular platform, they'll develop for it.