The issue isn't so much as the fact that *you* have access to *your* checked luggage, it's that you have *any* access to checked luggage *at all*. Unless you're going to completely segregate everyone based on whether they have checked bags or not before entereing the customs hall (good luck), it's easier, and "safer" (for whatever value of safety you ascribe to passenger screening) to re-screen anyone with an onward connection once they've entered a space where bags are available.

I'm hard-pressed to envision a situation where you would not be re-screened having passed through customs and immigration, regardless of the country you're entering. I cannot speak authoritatively on this, but I would imagine it's true the world over.