Why are flags part of unicode? I thought the point of unicode was to add something for every glyph ever written in every text so they can be stored digitally as plain text. Flags are... not text. And who decides what sorts of flags and valid which aren't? I mean... we know who.. .but humour me. (didn't read the article because the website is deliberately unreadable. zero guilt)
With emoji specifically, they were popular in Japan dating all the way back to the 90s, via carrier-specific encoding standards. The lack of emoji support in messaging was a reason that the iPhone and Android were slower than expected to take off in Japan, and so Apple and Google asked the Unicode Consortium to add emoji support, so they could have this feature on their phones while sticking to a universal encoding standard. IIRC, the Unicode Consortium was actually hesitant to do this and didn't want to be involved with standardizing pictograms into Unicode, but eventually relented.