katemason As Moxie put it, Telegram app on your phone is just a "view" onto their servers, where the data actually lives.
And as anyone who ever used it in the wild with 'regular' folks can attest, no one is using their Secret Chats. But to stay on topic, unlike WhatsApp which at least tries to put its metadata retention in semi-concrete terms involving time periods, Telegram privacy notice doesn't even make an attempt at that, basically saying they store what they store as long as it is necessary.
Ever-present Durov rants, their silly 'No-SIM Signup' and other blockchain nonsense also do any inspire any confidence in its future.
When it comes to E2EE messaging defaults matter as this study demonstrates. The amount of people I meet that insist on moving our conversation from WhatsApp to Telegram because 'it's more secure that way' is pretty amazing. Telegram's marketing has really done a number on a lot of people