Makes sense because the planets are so far away that a different viewpoint on earth won't make a noticeable difference. Unlike for the moon. This is why lunar eclipses are the ones that are only visible in certain places.
I don't think it is simply the "planets are so far away" that allows this to be visible from everywhere on earth. Stars are very far away compared to planets, and that distance makes them only visible from certain hemispheres (certain stars are only visible from certain hemispheres). I believe the fact that the planets are all on the ecliptic is what makes the alignments visible worldwide.
The large/small Magellanic Clouds are further away than the planets and yet are only visible in the souther hemisphere. The difference here is that the planets are all on the same ecliptic path.
Plus that they are near the ecliptic - comets may only be visible from one hemisphere (often plus some, but not all, of the other), even though naked-eye visible comets are typically further away than Venus.
You will not see this alignment if you are at the south pole or other points sufficiently south of the antarctic circle, either, given the time of year.
