I'm only 24 and i remember when we used to leave all the doors unlocked back home... all day long even when we weren't home. You just never had to worry about crap like that.
Yeah, I figure I pushed my luck on that last year. I lived in the middle of Toronto, and had a friend and his girlfriend staying in my living room. They were forever forgetting or losing the keys, so eventually we gave up and just left the doors unlocked (and sometimes open) for about 5 months (till they found their own place). Never had a problem, despite having about $15K dollars in mountain bikes sitting around, not to mention the computers, stereos, and CD collection.
When I moved here, the landlord kept stressing the security screen door. I was just "yeah, yeah, whatever" at the time, but about a month ago, my neighbour (that I share the steps and landing with) woke up to a noise, went to investigate, and caught some dude trying out the security door and windows of his apartment. He wigged out, started screaming, and the guy bolted. I'm a little more careful, now...
One of the ladies at work wasn't so lucky. Her and her husband had someone break into their place and rip off a bunch of stuff while they were home sleeping.