The thing the "Security" header is missing is, that if you don't power-up, there are other options you should take - such as moving your currency to a wallet, or an exchange, off of Steemit.
There's also a "savings" option in your Wallet, which locks your currency for 3.5 days, in case someone gains access to your browser or something. But the main point is, if you're not powering up, you shouldn't leave the currency just sitting there, and you do have other options.