In Matrix you've got to remember to turn on the encryption, and verify each of your clients. At least that's my understanding, maybe that is out of date.
It's also worth noting that verification is much easier these days given that cross-signing has been implemented.
Before you had to verify each pair of (sender, recipient) devices. This meant N*M verifications.
Now you only need to verify a new device when you are setting it up and each new recipient when you start talking to them for the first time. So it's N+M verifications.
In Matrix you've got to remember to turn on the encryption, and verify each of your clients. At least that's my understanding, maybe that is out of date.