Of the 100 adults you might know, directly or indirectly, how many of those have and use on-chain BTC?

That number / 10 sounds like a proper global adoption percentage.

I believe however that we won't need and most likely would never reach 100% onchin adoption for Bitcoin to dominate global currencies. Just like internet adoption didn't require everyone to manually send and receive packets of bytes. In its early days though, having enough techies and believers who built and used apps like web, file sharing, email, and others allowed the internet to be fully adopted later.