Why are e-ring bands thinner in the middle?

[Bridget]

At the bottom of e-ring bands, opposite to the center stone, why do the bands thin in? I have noticed this on a lot of bands, mine a little bit. Is there a reason for it?

 

[Nicrez]

If you mean the band that is above, in the line of sight, and NEXT to the stone:
It makes the band look thinner, and more delicate when there is a knife edge leading up to the diamond. All preference.

But I think you may mean the band that is below on the bottom of the hand:
Ease of bending fingers. The thinner it would be around the bottom of the finger, the more likely it feels "invisible" when you bend your fingers and those folds of skin are not blocked by metal...

 

[Bridget]

Yes, I mean on the back of the finger. Thank you!