Why not.It's completely safe if you are using hardware wallet or paper wallet.I'm not recommending desktop wallet as safe.Im using hardware wallets.If you're store your private keys,passwords on your pc,mobile or in web.It's a good chance for hackers.
I am very much comfortable to the technology behind any cryptocurrencies especially bitcoin because I know that my coins are safe in there. But I still have this in mind that whatever accounts that was made via internet and in online connection are hackable and you can be hacked anytime could happen.
well this is true that is why even that we actually have some security on it but because the internet are not safe then even that you take to invest here and you wanted to be safe then this may not be possible to be.