Earlier quoted context omitted.
NL is rather small sample to, say, larger countries like Poland that use SMS quite frequently. And depending on carrier, SMS texting most likely will be completely free with most of the current plans. Signal's rationale is just Signal's own reluctance to build an umbrella messenger. And given they do drop SMS, still won't introduce usernames it's very hard to actually sell it as a WhatsApp replacement. And now, with…
Being such a small operation, I think they're making a great decision by focusing on what matters most. "Most startups die by lack of focus". I very much believe this is their first public step towards breaking up with phone number based identity.
Currently, it looks like they are focusing on social networking features: stories, emoji stuff, better link previews. Basically everything that competition already did. The roadmap is not public, so I wouldn't take guesses as what may come next. But...
..."dropping support of X as a feature" is some kind of new transcendent approach to product development incomprehensible to common earthlings.