I'm also wondering how much coins got lost in exchanges.
People losing interest in crypto, losing passwords,forgetting how much coins they have, dying etc etc.
I would assume that this kind of "income" might be one of the major incomes of an exchange.
These coins are in no way lost. As long as an exchange operates, user funds work for the exchange. Furthermore, fiat banks dispose of their client deposits in favor of the bank if these deposits are not requested in the set time.