Your data, money or cryptocurrency is not stored on your device (phone, PC). It is on the blockchain network. You access using the private key. And the private key is already stored on your PC, phone or anywhere else.
And yes, the security of your data is very important poin. But remember, 90% security is a standard and very simple set of rules.
Why its important? Are you not afraid if your money is stolen by someone dude? whereas on the internet there are many people who have jobs as hackers? thats why security is important. You can't underestimate this, if you have experienced it, maybe you will be very concerned about this. starting from how to secure email, strong password, private key, your computer from viruses and so on