I'm a blockchain developer. Worked on a top PoS blockchain for several years then launched 2 additional PoS blockchains since. I've also analyzed many other PoS

I'm a blockchain developer. Worked on a top PoS blockchain for several years then launched 2 additional PoS blockchains since. I've also analyzed many other PoS blockchains over the years. Exchange wallets improve the security of a PoS blockchain because these wallets are high-exposure and community can be confident that the different exchange wallets belong to different entities. Because the ledger is public, existing big token holders can agree to HODL some % of their tokens if they are concerned that an attacker is trying to acquire 50% of all tokens. The main concern in PoS are 'sock puppets' - One person controlling multiple accounts pretending to be multiple different people (to evade detection). Because exchange wallets are well known, community can be confident that they are not sock puppets; this means that exchanges add some degree of security to the blockchain... In aggregate, those tokens are safe; it's extremely unlikely that all exchange wallets would be hacked at the same time (unless there is something wrong with the blockchain code).