"App installs" is a key metric driving valuations for SaaS/PaaS/etc. businesses.
Trading a useful product for dollars isn't that interesting. Collecting an open-ended, continuous stream of intel on a large population is fascinating - at least until it become generally accepted that this "intel", and the levers for manipulating people based on it, are really not that useful or effective (which is my own prediction).
Slack has the attention today, but the real poster child for this kind of behavior is Sonos - nowhere do you see such a stark juxtaposition between an actually useful product that people pay premium dollars for and pivoting the business model towards shady, sneaky, anti-customer patterns.