Who's to say? Security-minded Mac owners, perhaps? Last I checked, the best way to secure a machine on the Internet was to reduce the number of potential avenues for attack and minimize potential damage, i.e. by enforcing good security permissions and not opening any unnecessary ports. OS X *does* do this. (And comes will built-in firewall support, to boot, in case you do run any servers.)
If Windows *had* done this from the start, then there would never had been any viruses that can in minutes spread and make "zombies" out of hundreds of thousands of Windows boxes that only need to be connected to the Internet.
This is why a firewall and anti-virus are required software for anyone using Windows. And the inconvenience of Windows' permissions system (which requires you to log out and re-log in every time you want to perform an Admin/Power User action) basically makes it so that people say 'heck with it' and just run as Admin all the time, giving any potential virus or trojan escalated permissions with which to do its damage.
If you've got some real evidence as to how Apple and OS X ignores security, I'd like to hear it, but there's no point in speculating on something you know little about. (And you sound very unfamiliar with OS X's security policies.)
