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.