I did mine and the families in September for two reasons
My girls are now teenagers they need id, I dont want them carrying their passports around with them and losing them , because its a pain replacing them and the cost too.
2nd Also its easier to show, its photo id and in my opinion you get treated better from organisations and other places because it looks similar to the Spanish DNI
It was easy cost 12 euros and I'm pleased I did it, the girls, Richard, his folks and I all now have photo id.
I mentioned it to lots of folks and most of them have done it too. My Mum is next