>Sorry, it isn't enough to ask people to go looking on Google for random problems to prove your point. If you do have a recent example of a way to leverage non-privileged user shell access to root on a reasonably installed (for example, default configuration for a development station on an up to date(ish) mainline distribution, no "disable SELinux" nor "install random junk")
You must be very naive. There is at least one local Linux rootxploit every year, sometimes more often. Right now, no _public_ exploits exist that I'm aware of. But I'm absolutely certain that there are non-public exploits.