Because of habit, mostly. I am definitely coming to realize that the Linux development process does not produce trustworthy code, and further that the devs aren't really interested in security. They deride it as theater and want it to go away, while the security features in their kernel become less and less useful over time. At this point, getting user shell access on a Linux box is damn near equivalent to getting root.
Which means, of course, you get hacks like this one, and then a butchering of functionality because shell access can't be safely shared on a Linux machine.