The thing is that not all web wallets have this since the private key is need to be sure that the wallet app you are directly import private keys with storage options and particularly paper.
They can scan browsing history and caches in the system where temporary information is stored or even view your screen while you're generating your keys. Although seen as somewhat traditional, paper wallets remain a highly secure storage method, especially when used in conjunction with a reliable web wallet. It can be encoded in a number of different formats. Some people split paper wallets into parts that must be combined to reassemble the secret key.
