Putting all our coin in one place is very risky. Hard wallet is good and safe but if we lost it, its will be a problem. Better we store our coin in different place and keep our private key safe
Yes, that is what should be done by the people but there are times when some are just too lazy to separate their coins because it is bothersome for them to access different wallets so in the end they would regret not putting their coins in different wallets when their wallet is hacked.
We know that it is very risky to just put your coins in one wallet or exchange perhaps and if I have to choose between putting my coins in a hardware wallet or exchange then I would choose the previous one because it is much safer since I am the only one that has access to that wallet.