Why are the PCBs always on the negative or bottom of a cell. I would think that if it was on the Positive end, you wouldn't have the Positive strip running the length of the cell.
I agree. It seems that most cells are designed for the primary purpose of being used in battery packs (laptops and such), which use an external pcb. Single cell applications such as flashlights are a very small consideration when designing the cells.
Maybe it has something to do with the vents on the positive end? Also, cells always have a slight bulge on the top, adding a (normally speaking) flat board on top of that and a new button on top of that all that makes it even higher would make cells ridiculously long. Bottoms are normally speaking nice and flat.