Sure, I understand different tools for different use cases, yet people as a whole will gravitate towards what ever is easiest. So meeting people in the real world and swapping contacts, we do that in many ways, when we are at conferences, telegram is the place that is suggested to me most often to contact. 

This is purely out of convenience. This is where I find issue.  

Humans are creatures of convenience. 

Look at any grass in the city and you’ll usually find a dirt path cutting through it, while there is a perfectly good paved path to protect the grass and keep it nice next to it. 

It doesn’t matter what the defined use cases are people will use it in whatever way is most convenient. 

My point this morning was I wasn’t expecting to see signal under attack for enabling privacy by default for millions of people. My mom understands signal. My grandma understands signal. This is why it is effective. 

 I don't know what you refer with "signal under attack" maybe I missed some news?

I was merely steelmaning the case for "telegram friendliness" among bitcoiners.
Lately I always get in touch with people in nostr via SimpleX, no one mentions telegram for DMs.

Due to the phone number requirement, I think Signal is more appropriate for IRL friends and family, where your number and identity is already doxxed. Usernames don't quite fix this. 

 I totally agree, I use signal for daily driver with the people I trust, I use simplex/threema for others. 

Yet phone numbers are still the best web of trust that exists. 

 signal has usernames now 

 oh sorry I misread you, my mistake 

 Unfortunately tons of people do, I’m constantly inundated and redirecting people to better choices 🤷