I am the developer of userTrack[0] and so far more than 2000 customers/companies chose to self-host userTrack. Most of them are on the smaller side (eg. under 1k daily users) but there're also several that get 1M+ monthly sessions. To respect customer privacy I won't directly mention any names.
I also use userTrack myself and it just feels right to store all your analytics data on your own servers and not share it with 3rd parties. That being said, maybe the "marketers" would be more excited to switch to a self-hosted platform if it has some extra features (like session recordings, heatmaps, A/B tests, etc.) than to switch from GA to a private solution that only offers basic data.