So why do we need e2e encrypted messaging? Why do we worry about the "secure" part of messaging? One of the main reasons for me is, it's hard to trust a centralized authority.

Can you trust your information stored at your messaging app's servers stay secure forever? Can you trust that company to never get compromised? So yeh, they go through all the hassle of making things "secure" but attach everything to something(phone number) most of us can't get without revealing our actual details. So yeh, its ridiculous to go through all this hassle to make things private and secure, but force people to use something that de-anonymizes everything about them.

I don't want them to have access to my messages and make a profile out of me, even less of billions of people. That's why I also care about metadata: social graph is valuable for profiling.

I don't write anything that would be interesting to the NSA, I'm not a target for them, so I don't care if they see I use Signal.

BTW, say you have an anonymous Telegram username, I'm pretty sure it's trivial to find your name from the content of your messages. Or just from the metadata.