Even my hatchback has a pull-over cover that hides the contents.
Also if you're putting into your trunk do so before you arrive at your parking destination... many stories about people seeing you hiding stuff and then knowing there's something to steal.
We should expect, and be willing to pay for, better from our public services.
The cycle of moving mountaineering gear to and from my car solely to prevent theft uses up ~1/2 hr a week of my life, and provides utility to nobody.
I won't steal your stuff, even if you leave it in plain view in your car; it's yours. Please don't steal mine.
Looks like there's room for improvement in the US...
http://www.nationmaster.com/graph/cri_bur-crime-burglaries