other surveys that show that bitcoin adoption on the individual level isn't that high in El Salvador with over 90% of individuals not really using it to transact in the last years.
That is not contradicting with the conclusion made here though, because there is a difference between "owning bitcoin" and "wanting to transact using bitcoin". A lot of people are HODLers who aren't going to spend their coins, so their respond to the first question will be "yes" and to the second "no". You can't make the conclusion based on second question that they don't own bitcoin.
Bitcoin owners have not moved bitcoin in the last years contain two possibilities.
These people are holding their coins by two possible reasons: believe in Bitcoin future and proactively holding bitcoin; or have no belief in Bitcoin future but don't care to sell it or do anything with it as perhaps their bitcoin portfolios are small.
The second possible reason is these people already lost their bitcoins. Like El Salvador distributed bitcoins to their citizens' Chivo wallets and some just lost that wallets together with Bitcoin in their wallets.
Lost bitcoins are donation to everyone like satoshi said.
Lost coins only make everyone else's coins worth slightly more. Think of it as a donation to everyone.