Would that be surprising to you? I assume you might be an American - I was really surprised when I visited the US and noticed that most people use unlocked boxes located outside of their houses to get their mail. Where I live people either lock their mailboxes or they get mail through a slot in their locked door - nobody leaves their mail accessible.
Mail slots are typically used in America in all row-homes (aka, very nearly all houses in towns or cities). Apartment buildings almost always have locked mailboxes, unless you are really scraping the bottom or your apartment is in a converted row-home (my old apartment had a single mail slot on the front door, the 3 different apartments just sorted each others mail). Private developments often have locked mailboxes outdoors by the entry gate.
Unlocked mailboxes outside the house really only exist in rural areas or regular suburbs (to be fair, these sort of homes probably make up a plurality of homes in America).
The bigger problem is what happens with packages. Unless you live in an apartment building with a staffed leasing/mail office, chances are your packages get left by the door (usually in plain site), or you need to be home to sign for them.
Well, in the US it's a substantial federal offense to steal mail or to read someone else's mail (coughunlessyouarethegovernmentcough), so that acts as a big deterrent, I think.
I'm not sure, but I'd assume that if you go around stealing packages, you're probably not doing it just because. You're doing it systematically for financial gain. In which case you have to be a repeat offender for it to make sense. In which case it's easier to track down. This happened near me last year:
Would that be surprising to you? I assume you might be an American - I was really surprised when I visited the US and noticed that most people use unlocked boxes located outside of their houses to get their mail. Where I live people either lock their mailboxes or they get mail through a slot in their locked door - nobody leaves their mail accessible.