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.
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.