You're absolutely right that the appropriate level of security does depend on someone's threat model, but I do want to point out that you don't need to be an activist to benefit from privacy.

I'm a really big fan of the airport bathroom analogy. When you use the restroom in the airport, you close the stall door behind you.

You're not doing anything wrong, you have nothing to hide, and everyone knows what you're doing. But you take actions to preserve your privacy anyway, and that's good.

Everyone deserves privacy, and the psychological comfort that comes with it. Dance like nobody's watching, encrypt like everyone is :)

That's not the point the GP was making. They meant "I'd rather give up a bit of privacy for a big increase in usability, as I'm not in the group of people that needs extreme privacy". I happen to agree with them, I get more benefit from a fairly-private messaging app my friends can use than from an extremely-private messaging app nobody in my social circle can use.