Why don't Macs have to be patched?

They do! Apple plugs ten 'critical' security holes

More fixes for OS X

Tom Sanders in California, vnunet.com 23 Sep 2005

 

Apple has released a security update for its OS X 10.3 and OS X 10.4 operating systems.

The patch fixes vulnerabilities in the operating system itself as well as bundled applications.

Apple does not provide severity ratings for the flaws in its software, but an advisory from security website Secunia gave the vulnerabilities its second highest rating of 'highly critical'. 

Full story.... https://www.vnunet.com/vnunet/news/2142729/apple-plugs-ten-security-holes