Windows is a wasteland of garbage, of unsigned applications from shady looking sites, where telling the real thing from a malicious fake is often very difficult, even for experienced users.
If you're not familiar with the application in question and just Google for it and download the first match you can get burned very badly. This is generally not the case for OS X since the applications tend to be more tightly curated.
Consider Panic Software, makers of Transmit, which comes signed by the developer, and Filezilla, which generally comes from Sourceforge. The official site for Transmit is well maintained and offers a no-nonsense download link.
For contrast, the official download for Filezilla, an equally popular FTP client for Windows, came with malware bundled in due to SourceForge's bad business decisions. If that isn't a sign of a completely dysfunctional software ecosystem i don't know what is.
In the Windows world people are constantly battling this sort of garbage. In the OS X world malware like this is a shocking anomaly.
It's still insane to see what consumers put up with, seemingly without even noticing. MS of ca. 1995-2010 has created an ecosystem of tastelessness, where a new computer can come preinstalled with competing "Printer managers" or whatever and, without even doing anything stupid yourself, you can't use it for more than 10minutes without being interrupted by some update, "virus warning", "expiry warning", "system optimization" etc. It's truly baffling.
I've seen almost zero evidence of this. The state of affairs is worse than ever. There's non-Microsoft efforts like Ninite (https://ninite.com/) that work to fix this, but that's fighting an impossible battle.
Microsoft's core security has gotten better, the days of them casually trusting anything that ends up on your computer is over, but this has lead to a culture of flagrant abuse of these features. You constantly have to run things in Administrator mode, click dialogs that present scary warnings, and you end up numb to it.
The real detriment to the experience on the Windows side is how loaded down with absolute junk your average OEM system is. They're pre-loaded with malware, with deliberately broken software, with trial versions that nag you constantly, and drivers for inconsequential things that always seem to need your attention regarding an update or a settings problem.
Microsoft is in a tough spot when it comes to cleaning that situation up. Most PC vendors depend on the money those "services" provide, their margins are sometimes negative without them. This is part of the PC industry's suicidal race to the bottom that keeping prices low at the expense of user experience.
On the OS X side, by comparison, alerts like that warrant a bit of attention since they're so infrequent. The Software Update thing can be a bit of a nuisance but telling it to shut up isn't hard. Linux and BSD are likewise pretty quiet, and alerts stand out as a total anomaly.
I disagree with the money analysis... there's a reason those spam emails from a Nigerian prince contain intentional misspellings; it's to act as a filter to filter out the people that would not fall for the scam so as to not waste the time of the scammer. Higher levels of affluence correlate(not cause of course) with higher levels of education[1] so it's probably a less effective target just on that point alone. I do agree that Ransomware will be a more lucrative form of malware on OS X per 100 machines infected though for your reasoning. More money, more valuable data, more incentive to get the decryption key.
[1] http://www.nytimes.com/2012/02/10/education/education-gap-gr...
Apple's sandboxing technology is supposed to prevent this, but sandboxing is optional on the Mac.
