It is an obligatory component only for a "component based engine "

If you define a class Actor which contains a variable such as " position " or a method such as " Move " then you dont need to have a class Transform
You simply write, in the Loop() function

myBot.position;
myBot.Move();

instead of attaching a script to myBot :

transform.position;
rigidbody.Move();

You are right 3dgs is basically a component based engines but in the past there were engines with a different archictecture
,ex TrueVision
Having said that , I dont mean that components are bad, I mean that in my opinion they lead to a ugly code

I did hope that UE4 resumed the old fashion programming style