The other responses talk about the zinc crystallization, but I wonder if you mean something else. Do you mean how sheets of galvanized steel often have a pattern of indents, maybe in two perpendicular or close to perpendicular angles, and some galvanized steel is smooth, like hand rails or guard rails on a highway?
If so, the indents, or embossing, help with traction when walking on it, help keep it rigid, helps water flow off it, and other benefits, while a hand rail or guard rail doesn’t benefit from any of that, so why bother spending the money embossing something that is at best aesthetic and at worst actively detracts from the function.