That is a function of the game. The devs did that, and the reasoning is that if you have map contacts on, you can far too accurately draw things to make it "fair" for the enemy. Therefore, once you zoom in a step or two (sometimes 5x) from the max zoom, depending upon the element you are using, things will disappear. This is also why your ruler only gets down to a 500 yard or meters resolution before it either jumps up or down to the next "rounded" figure.
