No it is because of how a UNIX based OS, in this case BSD, handles software packages. OSX has something like a 15% market share, that is something like 150,000,000 computers. On a non-enterprise Windows system the end user is encouraged to run as administrator and the way that Windows handles packages, you can randomly install anything you like from any source or more importantly a malicious piece of software can also. You can't do that on a UNIX based OS, so they don't bother.
I am running a custom Debian based OS, Linux Mint Vanessa with a Xanmod RT Kernel. If I install a program using the OS' default package manager it will have to come from a digitally signed repository or PPA, so a virus isn't coming from there. If I decide to install an app via Flatpak or AppImage, it will run in a sandboxed environment so it cannot affect the underlying OS, unless I physically tell it to. The only way a virus could get into my system is if I compiled the program from the source code or manually installed it via a *.DEB file. The same is true on OSX.
Myself and my Oncologist would disagree with you. I got smoking related cancer from smoking weed. It is a fact that burning any organic matter will produce tar and other carcinogens, if you then inhale them you stand a higher chance of developing cancer. You don't need a specific study into smoking weed as the results of regularly inhaling smoke from burning organic matter is well documented.