All other t-shirt styles are unnecessary. Think about it.
When you're wearing a business shirt without a tie, you need the top button open, and you really don't want your high collared white t-shirt rim sticking out for the world to see. It cheapens the look.
So since the v-neck t-shirt style still works in a lounging day around your house, why would you buy the other kind?
Just buy the one that works in every occasion.