This is hardly unique to Magento. Lots of applications do this. It's not ideal, but it's not SO bad if the application nags you to patch on start up. I don't use Magento, so I'm not sure if it does.
Joking aside, they are going to release 1.9.2 soon. For Magento 1 they're still doing feature releases, and they do patches for everything else because store owners do not like going through the upgrade process.
The only problem arises when people download fresh versions.
(or even worse; one-click installers on some shared web host... so they can't update it even if they wish!)
In fact, Magento issued two notification messages, on Friday and on Monday, so even if you applied the patch after seeing the first message, you still saw the second message and experienced that brief moment of panic.