I spent a summer reading criminal court case files in a county that combined rural, suburban and urban. Regardless of locale, most home crimes were the result of a criminal taking advantage of an unwary household occupant. They were either opportunistic in that a criminal saw an open window and took advantage of it or he was out trying doors/windows to find those that were unlocked.
Having read endless reams of paper describing burglaries, assaults and rapes that occurred in homes with unlocked doors and windows, there is no way on earth I'd ever leave either unlocked. I cannot tell you how many times I read, "I never leave my windows open, but it was so hot that night, I thought I'd take the chance...."