Its all about tradeoffs to me. Spam is a real problem on every messaging service. Even those that require numbers. I get zero spam on Signal. I get quite a bit on Telegram and I got a TON on Skype back in the day. For the women in my life spam is even worse. I don't think it helps to belittle spam as an actual problem. Spam has really degraded the effectiveness of email for example.

I don't think we should be fan boys and girls for Signal, they have their faults but lets also recognize they have built a very good messaging app that is used by a great number of people around the world that don't have other good options(I know alternatives exist but none are as familiar as Signal). I have tried to move people on to Signal or other alternatives. Its not easy to do. I have had the most success with Signal by far.

They also have a target on their back. Lets not let perfect be the enemy of good. I'm very glad they have added this feature and I hope they will adopt bitcoin as an anti spam measure in the future. Seems like a good option but I don't think its a practical option for them yet. Not from their perspective at least.