Taking it up after it became available is not the same thing as asking for it. Sorry but this a frivolous cosmetic thing compared to security issues like Signal's ongoing linkage to phone numbers.

That is correct, but "nobody was asking for stickers" isn't, and that sort of thing does dramatically affect adoption. Also, in the cases I am talking about, not using an app because it doesn't have a feature technically does mean they didn't request the feature, but I'm not sure that is a useful distinction if our goal is to get people to use more secure methods of communication.

I really can't buy the proposition that demand for stickers outweighed the years-long pain points about things like your Signal identity being tied to your phone number or a ping going out to everyone in a person's address book who already used signal, both of which are at odds with the core mission of secure and private communications.

Signal's "ongoing linkage to phone numbers" is one of their more powerful security features.

Why is that? Not disagreeing but genuinely curious. One of the issues I face sometimes is wanting to stay in touch with someone I met. I'd like to do that over Signal (I don't use any of the popular social media platforms) but I don't feel comfortable sharing my phone number with them. It would be nice if I could use a unique user handle instead.

It allows Signal to work similarly to the messaging services it replaces without having to keep serverside contact lists. Those contact lists, which practically every other "secure messenger" keeps, are the most valuable metadata the service keeps, in many cases more than the content itself: they're a record of who talks to who. Signal's phone number system means they can keep those contact lists clientside by piggybacking on the device contact list, which is keyed by phone number.