why do i still have margins if i play a widescreen movie on a wide screen tv?

Answer 1

That's the design
It won't be an exact match because it's an approximately what is shown in the theater
Actually, I prefer widescreen to fullscreen
Widescreen is what the filmmakers shot
Fullscreen cuts off parts to fit into the full TV screen
So, it's a personal preference

Answer 2

Margins on the top and bottom are normal, because many theater movies are wider than a TV 16:9 ratio. To keep the accurate theater representation, the TV displays it with black bars at the top and bottom.

Now if you get are getting them on the sides, then something is definitely off.