content: It's a volume problem. When most people are using Windows OS, security hackers have the greatest incentive to circumvent Windows' security.  Which means Windows' security will face the most scrutiny, and have the greatest consequences if it fails.  Apple has had similar problems since the iPhone took off, and Linux/Google have had more problems since Android has grown. The software hasn't become poorly designed, but it's lost the 'security of obscurity' which protects mistakes in less popular software.