Easier just to say it's a thing, like a force of nature.

New network growth (mobile, Africa, Asia) uses it, old growth stays on v4 and will eventually roll over. People with address space usually don't need much more, but the IPv6 space better reflects how connected the world is - we're gonna need a bigger address space than v4, that's for sure.

New protocols shipped quickly on rough consensus and working code and weren't perfect - some left all kinds of undefined behavior, or lacked clear advantages over predecessors and competing protocols.