Bitcoin is not vulnerable to theft but maybe your wallet, the bitcoin on your wallet can be stole by just hacking. Using a hardware wallet is assured to safe your bitcoins so that no hackers can access to you wallet. Use two authentication when logging in your wallet to avoid wallet being hacked.
That's why you must put all your attention into finding the best wallet best suited for you. IMO not everyone uses hardware wallet cause they still didn't know what's the capability of hardware wallets. Based on my research Trezor is the best secured wallet i've known let's just say hardware wallet is not appreciated by many individuals true hardware wallet isn't cheap but it has the most secured grasp of what's your's some of us take this for granted some aren't lets join the people who aren't taking this for granted other than losing all your money with the good old normal digital wallet.