There's nothing wrong with tracking raw downloads, but for investors who are used to social media in which you 1) target specific people based on their interest

There's nothing wrong with tracking raw downloads, but for investors who are used to social media in which you 1) target specific people based on their interests with ad-like content that is generated to resemble those interests 2) track every conversion event those specific people do in your funnel, it's a far cry. And of course, those two criteria above are why social media became such a huge business, because that's more efficient than a radio ad, or a download count. I'd argue that these examples of great content are great precisely because the creators can't track their audiences very well. Their audiences have a vote every time they download.