no one can rob it
This is false... your cryptos aren't 100% secure and they can be robbed. Let's say you have your private keys on your home in a paper wallet, and a thief joins to your house and steals those private keys, another example is, let's say you have your private keys in your computer, and you download some software with a malware, that way your keys can get rob. And a last example, let's say you work hard on security and no one can access to your private keys, but sadly a user finds your private key with brute force.
And here's where conscious and responsible holding comes into play. If you leave your car parked in a dark alley, chances are someone will steal it, but there can be many ways to minimize the possibility of theft like adding a hidden button that cuts off the ignition. It's the same with bitcoin. If you hold your private key or seed on a piece of paper or your computer it can be stolen, but if you memorize your seed, or put it on a metal plate and hide well, it's almost impossible that a thief will spot it and know what it is.