Well, viruses have hit cellphones.... And the Mac has quite a huge installed base - 5% of e-friggin-normous is still a huge number.... And there's the opportunity to let a lot of air out of the viewpoint that the Mac is more secure.
That adds up to plenty of motivation to write a persuasive Mac OS X virus.
All you offer is speculation. All we offer is results. Some "professional" - ha!
No, I offered facts in my link on OS X vulnerabilities...did you not read, or are your eyes failing your brain?