Guessing most/all cases are this way due to camera lens. And speaker holes.
But, there are cases that allow you to go the other way, if willing to sacrifice sound or camera. I have a case where it's a basic sleeve, so can flip either way. Or if using in correct insertion mode, can always use the lid to prop it in a tent like shape, so button's on the left.
For example, I bought something l
ike this.