It's older than a lot of new developers at this point.

For a little historical context:

• IPv6 became a draft standard in 1998, and did not officially lose the "draft" status until 2017.
• Hurricane Electric launched their well-known IPv6 tunnel service in 2001.
• Google has published IPv6 adoption stats since 2008. These stats consistently show a greater fraction of users are on IPv6 on the weekend, because it's more common on mobile and home networks than office networks.