Why is it rare for frames to be completely accurate?

In a statistical analysis, a frame is referred to a list of individuals present in a population. The frame is a list, which is taken pre analysis of any data for that particular population.

Everyday, many individuals get added and removed from the population one is studying. So, one can say that the frame is very dynamic. Hence, it becomes difficult to count a perfect number of individuals present in a particular population. This is the reason, why the frames are rarely accurate.