XRP Ledger has a reserve requirement of 10 XRP, which is a minimum amount to store on your address. 10 XRP is used to activate your address and permit sending/receiving operations. It is an unspendable balance – you can’t withdraw it. To be able to manage XRP in Coin Wallet, you have to deposit 10 XRP on your account.
Why XRP Ledger has this requirement?
XRP ledger uses 10 XRP unspendable balance as a restriction measure to prevent the shared global ledger from growing excessively large as the result of spam or malicious usage. To submit transactions, an address must hold a minimum amount of XRP in the shared global ledger.
Why centralized services don’t have this requirement?
Exchange services provide one paid address to many accounts. These users do not have their own unique address but only their own Destination Tag which assigns their accounts to that wallet. And hence, no activation needed from the user’s side. However, users have no control over the addresses. Coin Wallet creates a unique new address and gives the user full control over it by providing access to private keys.