Classification is often changing! after introducing the domains this video shows 5 kingdom and 6 kingdom system. why is classification subject to change?

The classification is subjected to change due to the increase in scientific knowledge with time.

As scientists make novel discoveries, the grouping of organisms changes according to it. For example, at the time of Aristotle, the scientific knowledge was not much advanced. Hence, at that time organisms were simply classified as plants and animals.

With the passage of time, as scientists learn and discover, the scientific classification changes based on these new studies.