Few reasons:

1. Habit. We're used to use Telegram for everything: news sources, social network, messaging, memes. Telegram has more capabilities than other apps. You can't realistically move your family and friends to another messaging app because of all of that and the network effect.

2. General attitude of all people towards privacy and sharing data: they don't really care. It's "Who would even care about my data?" and "I've got nothing to hide" all the way.

I doubt most of people ever thought about the topic of trusting a messaging app. It's not the framework they operate in.

There are two global psyops done by I don't know who:

1. That Bitcoin is safe and anonymous.

2. That Telegram is super safe for whatever shady or private stuff you want to do.

One of the best marketing campaigns ever.

I would also want to use this chance to alert everyone who uses Telegram that:

1. It's not e2e by default.

2. They use proprietary encryption protocol. You don't have access to code.

3. I don't think Telegram is profitable, I don't know how it can be with that scale. Which makes you wonder.

4. If you open in-message links, you have a chance of losing your account to hackers thanks to the old vulnerability that hasn't been fixed for years. You literally have to check the list of devices connected to your account every 12 hours if you want to be safe.