You believe that users should have to check the status of Cryptopia's wallets before sending a deposit there? Each and every time? Ridiculous.
Yes - that applies to every exchange. Don't send crypto to wallets that are in maintenance - it is common sense.
That's nonsense.
EDIT: Somehow posted before finishing.
Transactions are registered with the blockchain using the addresses in the transaction. A wallet then syncs with the blockchain and recognizes any transactions on the addresses it keeps track of. Nothing is sent directly to any wallet. It's all done on the blockchain.
EDIT2: In case that wasn't obvious, just consider the fact you can completely delete your local wallet and all the data it keeps locally, but still recover access to your assets from the blockchain if you have the private keys for your addresses.