We all agree there is nothing wrong with looking like a tourist for fashions sake, but for security sake some of us feel that by standing out a wee bit less as "a hick from the sticks" that we may be a little less likely to be targeted by beggers, pickpockets and scam artists.
Case in point, I have read posts by people claiming they were accosted by scammers( the ring trick and the do you speak english approach) several times in ONE day.. I on the other hand have only been approached twice in many, many trips,, I am not sure, but I think sometimes it is better to look like you fit , or at least like you didn't just fall off the back of the potatoe truck.
Ultimately everyone should wear what they want, but if they ASK.. then don't expect everyones answers to be the same.