All these (ad)ons always take priority over performance.
This is US defaultism. People doesn’t care about sms capabilities outside the US. The US isn’t a huge market for Signal.
I think it did effect things. SMS is weirdly popular in the US (i think it’s might be cause they didn’t use it much in the 90s?) but people I know in France and UK still use texts for some things, even if messaging apps are where most of communication happens (French people even use mms which is insane).
I know that I managed to convince a number of tech-shy people (including parents) to get Signal by telling them replaced their sms app, so it wasn’t a whole extra app / network they needed to use. It was great for me because I could ditch WhatsApp completely. But when signal stopped supporting sms they went back to just whatsapping and texting, so I cracked and reinstalled WhatsApp to keep in touch with them.