For the same reason why use EventBlueprintUpdateAnimation (the function is called every tick too) in AnimBlueprint
The character’s status needs to be updated, character can suddenly jump, fall into the water and so on
Also, you can very easily change the current animation that plays in each machine. There are even 2 special classes for these purposes - so for updating animations too.
Also, data need to be updated - let’s say Blendspaces, …
You can also do branching using your variable and use different MoveMachine for each branch(Let’s say you need special animations when you run with weapons in your hands and without them). This also requires a real time update.
These machines, by the way, are macros, and there is a workaround in each of them.
Plus, if any machine captures the calculation, then the following machines are not called at all
Here you can make a small optimization - call not every tick, but let’s say through the tick
Especially for AI who moved away a long distance from the player