IME operators startefto do CGN for legacy IPv4 when they started offering v6 by default to mobile & consumer fixed lines.

Fixed line ISPs who use cgnat typically have ipv6, tho.

I's 50%, i would not call that "not a thing in many countries" For mobile, it does not usually matter, you have a smartphone, where you would not host something.

For a huge percentage of the developing world the only internet connection people have is a smartphone, and dedicated residential internet at a fixed address is only for the upper middle class and the wealthy.

It matters for smartphones too (think video calls, IoT applications, and home/office networks that have mobile network as uplink) but fortunately IPv6 is common there.