We all know that in the early years a lot of bitcoins were lost because they were worth pennies, most people didn't even imagine where this could go, there was no HW and things like that. But even though the bitcoin loss rate has been reduced in the last years I am sure there will still be human errors like the one in the quote that will end up with bitcoin loss, which is not bad for the rest because as Satoshi said they are like a donation.
People lost their bitcoins, already lost their coins, they possibly felt sad about it or were not disappointed at all.
Their lost bitcoins, with us, are gifts as Satoshi Nakamoto said.
Lost coins only make everyone else's coins worth slightly more. Think of it as a donation to everyone.
In the past, people did not have big reasons for making wallet backups and they did not know importance of wallet backups. In recent years, more people know about it but in practice, they can do it very badly and ignore basic steps. It's hard to teach someone and give them enough motivation for doing good practice at beginning. They usually want to experience it by themselves, learn lessons and after all will remember about lessons they already learned.
How to backup a seed phrase? It can help someone but can be meaningless with others.