Pretty dodgy approach though, because there are various services that provide Bitcoin "functionality" for many users with a handful of wallet addresses, or use many different wallet addresses to mix/launder transactions.
Another way I estimate usage/adoption is looking at Google Trends and comparing it against something I can use as a baseline (in my case "reddit"), right now Bitcoin averages around ~30-40% of search query volume compared to reddit [1] (and even more if you look at worldwide queries) which is obviously not perfect comparison, but is an interesting datapoint.
1: https://trends.google.com/trends/explore?date=today%205-y&ge...