It is a missing feature for WP stats and now it is available on wpdevmetrics!
Since there is no API for getting historical data about active installs of the plugins from WP, we were forced to track that changes on our own. When you register the plugin on wpdevmetrics, it's automatically getting tracked on a daily basis. For all plugins that were registered previously, we started tracking active installs since November 2019, so you may have some insights already ;)
This feature is available for all paid plans. Check it out and stay safe!