According to the data I'm seeing, less than 10 million addresses have more than 0.01 BTC. Nobody knows how much of that is artificially inflated, since a single person can have an unlimited number of addresses.
https://bitinfocharts.com/top-100-richest-bitcoin-addresses.html
Even that isn't "adoption", it's almost entirely speculation = looking to sell to the greater fool. Pretty much nobody buys or sells goods/services directly in BTC because it doesn't work well as a currency.
Using your metric, less than 1 million BTC addresses hold amounts that aren't tiny.
They have companies specializing in chain analysis (which the US government uses for tracking and the IRS recently signed up with to track top crypto blockchains) that analyze how addresses interact with other addresses, i.e. my bitcoin wallet has over 50 addresses ranging in balances from small to several btc's, some are change-addresses auto-generated when making transactions
What has been the big trend as of late is that many of the holders use a "shared" wallet approach, aka custodial wallets
For example, Coinbase has 68 million users so let's say 50M of them have some bitcoin balance and keeping at their Coinbase account, then all the known Coinbase bitcoin wallet addresses are in actuality representing 50M bitcoin holders
Repeat the same process for PayPal who does not even allow bitcoin/crypto withdrawals. How many of the 300M PayPal users own bitcoin/cryptos. Rinse/repeat for eToro, Robinhood, Square, IBKR, etc
This is not the preferred way for owning bitcoin/cryptos, but it's the most convenient one that has brought massive amount of users to the space
