We aren't. There's a variety of reasons people choose to use v4 (some good, some bad), but you don't have to.
The network my desktop is on doesn't use v4. It works. v4 isn't a required dependency.
How do you get to github? How do you connect to news.ycombinator.com? Why is an IP address more valuable than an IPv6 address? Why is IPv4 the incumbent 30 years after IPv6?
Indeed. And many mobile networks are also v6 only with a translator like xlat at the edge for compatibility with anything still on v4 only. And since so many people get internet only from mobile this is becoming a norm.