It isn't a selling point. It was launched without a one time purchase option and was added when so many people immediately asked for a lifetime purchase instead.
It's pretty high when apps like Lumafusion are a one time purchase of $30 or $20 during sale. And then there's procreate at $13. I guess I just don't value social media apps that much. Especially when the browser or Foss alternatives have been sufficient for me that don't have any ads in the app itself to begin with. Which is a reason I've always preferred separate apps like reddit is fun platinum over IAP approaches to removing ads from apps.