Why do people scrutinize me for wanting look nice?

Like we will be going to Village Inn (A resteruant) and my sister will be like "Their are no cute boys so i don't see why you are getting ready to go see frumpy waitresses and octagenarians." I then say because I like to look decent. I mean not like glamorous but at least do my hair, makeup and put on clean clothes! They act like I always do this too impress people! Does anyone else just get ready for yourself? To look good for you not for anyone else?