[mgbmtl]

IPv4 has a lot of complexity:

- NAT and CG-NAT for big networks is complex, resource-intensive.

- Fragmentation on IPv4 requires more work/complexity from routers.

- Some of my friends seem to think that calculating /29 IPv4 networks is simple, but I don't deal with this often and it really annoys me (yes, even with ipcalc). Not to mention the number of addresses lost due to routing (I often use link-local addresses on IPv6).

Start moving now, progressively, or you'll be forced to do it in a rush later on. This isn't too different than https adoption. Those who minimized its importance ("oh, that's just internal communication, it can be plain http") got seriously bit.