It’s also important to have an option to turn it off, to benefit from mass-grouping (whatsapp limits groups to 256 users, lurking or not), chat history (new group participants can’t scroll up in whatsapp) and easy continuity (phone/pc job use case). Also it is not clear if whatsapp implements the same:

  - forward secrecy
  - self-destruction
  - forced destruction

as telegram does. E.g. whatsapp seems to only have an option for 7 day self-destruction, which may be too long for some use cases, and no instant destruction. Neither of two are superior privacy-wise all things considered, but stating that always-on e2ee is a most important thing is probably naive. And then you have tg bots, ui/keyboards, stickers, etc which for a regular user outweigh the security area entirely.

Also your virtual bet is lost because every time my circle discusses ‘hot’ topics in telegram (company issues, lawyer/audit-related chats, recreational drug use, etc), we go secret and warn users who do otherwise. We can’t check whether that is common or not, because those who have to be ‘secret’ may resist to admit this activity.