Would you put your baby in this as an undergarment?

[Stilton1]

Would you put your baby in this as an undergarment at 3-6 months? The reviews are all 5* and comment on its softness, but I don't know if it's more of a summer 'top', or underwear/vest to go under other clothing...

Most babies ( in the western world and beyond) wear these don’t they?
It am I missing something?

Babies' heads are bigger than their bodies :o So it doesn't matter what opening you get, you can always take stuff off by pulling it down if needed.

I don't understand why back buttons are better for slim babies (than front buttons? No buttons?)