They are shaped that way because the tip of the stick, often called the bead, provides an even, consistent sound when hitting cymbals or the drum. The butt of the stick, or the handle is shaped to give the drummer something to grab while still giving a even sound via the bead.
Playing with the butt of the stick gives a rawer, more trashy sound. Not good for jazz.
Yeah, I’m a drummer, and I can tell you there’s a HUGE difference in sound between the end with the “bead” and the “butt” of the stick. Having that “bead” at the end is a lot more precise, and makes it easier to place notes. It’s also fatter around the end not only to give the stick more weight (therefore better velocity) but also a better grip.
I am a drummer, too. the real answer is less weight at one end. having a solid piece of wood would be heavier and you could make those fancy drum licks without one end being lighter than the other.