It's funny because displaying bitmaps in a terminal-like interface has been possible for many years. Even TempleOS[0] can do it! But somehow it's just never caught on. But the unicode thing works because it gets shoehorned into existing standards and functionality. Legacy is a bitch. "The things you own end up owning you".
Makes me wonder, though, is there enough space in unicode to just encode every possibly 16x16 bitmap? 256 bits?