Element seems to be focusing more on the IRC/Slack/Discord style of communication though instead of Signal/WhatsApp. You can definitely use it for the latter (I use it for plenty of 1 on 1 conversations with RL friends) but right now it's more for channels and rooms and eventually Slack workspaces/Discord guilds.
That's all on the client end though; I'm sure someone will eventually write a Matrix client that mimics Signal/WhatsApp etc more.
The relationships between the home server, identity server, and client on Matrix are not made clear in any user friendly way in the Matrix documentation for homeserver operators so I can't imagine it's clear for end users either.
It's one of the things that I think keeps killing Matrix. Now let's see if Arathorn shows up to tell me how wrong I am. Wouldn't be the first time. Nothing inspires confidence in the maturity of a product like a CEO that joins discussions to tell users who've had bad experiences that it was their fault for not understanding the documentation. That's how Facebook got so big, don't you know?
I'm absolutely obsessed with chat solutions like Matrix and Arathorn probably doesn't remember me but I remember his attitude towards my feedback.
You may want to consider how your (seemingly legitimate) comments about the documentation might sound to Arathorn, who is obviously working hard to engage with the community and owes you nothing. For comparison, Arathorn seems to have engaged constructively with other more polite comments in this discussion.
I hate all the messengers that make you friends rat out their full phone address book (including your private phone number!) with a passion and I am very glade Matrix has not succumbed to this predatory practice like many others.
If you're interested, https://github.com/vector-im/roadmap/issues/10 is the relevant issue on the public Element roadmap: https://github.com/vector-im/roadmap/projects/1
If someone gives me their phone number I would find it to be extremely rude to them if I just pass it to some third party without their consent. And most people likely do in normal life:
"Hey Bob, can I give your phone number to Alice ? She would like to buy that furniture you re selling."
Yep people will just give their full phonebook to a third party so they can see who else is one the service (and betrayed their thrust by giving it their phone number!). I really hope this is just UX dark patterns, where the apps ask for phone book access but don't explicitly tell users how they are doing this matching. Users doing this willingly would be much worse...
What good is a phone messenger app if I can't send someone a message on their phone number?
Signal just works, I use it as my day to day sms app, and it shows me who of my friends also have signal so I text them on messenger if they do, and WhatsApp if they don't.
So the real reason is Matrix just isn't even trying to compete with signal or WhatsApp, it's competing with MSN Messenger, which everyone stopped using over 15 years ago.