Yeah, they put grills in all the cars so that they can use the same design of door panels for all interiors, regardless of sound system installed. This is a pretty common practice, especially when door pillar trim and/or lower door panels are molded plastic. It costs hundreds of thousands of dollars to make alternate molds to produce the "speakerless" door panels or pillar panels (basically, they need tools to make two different versions). Also, if they did choose to produce panels without the grills, they would have to manage inventory of many more SKU's (stock-keeping units) in inventory for production at multiple plants. This leads to a lot more cost and inventory investment. The auto manufacturers will change a supplier over $.0001 per part (yes. . . one tenth of a cent). I've been on both sides of that situation, having worked for an auto parts manufacturer for over 20 years.
Oh, and those "fancy looking" speaker grills . . .they cost next to nothing, so it is really cheaper to put them in than to change all the parts to leave them out.