In The Name of Allaah, The Most Merciful, The Bestowed of Mercy

Every person is likely to be judged by the one he meets based on the clothes he is wearing, and likewise will judge him based on his actions, speech, statements, sense of humour and composure. Shaikhul Islaam Ibn Taymiyyah [rahimahullaah] said: “The people are like a flock of sandgrouse with an innate disposition that makes them imitate each other.”
This [statement of Shaikhul Islaam is] true, and that is why when a new type of clothing appears, you find the people rushing towards it. And it does not take long for all the people to seek after it [or accommodate it]. As for a Shaikhul Kabeer [i.e. a very old person] wearing the clothing of young people, this is among those affairs that are not befitting.

Sharh Hilyati Taalibil Ilm’ page 65 – 66
abridged & slightly paraphrased