Curiously, I'm not speaking of style in any metaphorical or even intellectual sense, but the commonplace idea of style in clothes and hair such superficial nonsense. For which I see some unexpectedly positive functions.
I won't pretend to be an expert on style. To the best of my knowledge, the acknowledged experts only know what they wish the styles would be -- and not what the style actually is. The only people who know what the style actually is are the people who live with it, and from what I've heard the teenagers can't agree, either.
As far as the current observation is concerned, I am thinking primarily about why styles change. Why do styles change? Why, to be different, of course. But why be different? Especially in the matter of clothing or hairstyle, where the obvious reason for having a style is to conform. (Otherwise, why not just do what you like?)
And all that mental and emotional effort spent in thinking about style! What's the point? My suggestion is that is the point. To be somewhat less obtuse, I suggest that one point of style is to raise awareness of one's own body, of other people, and of the connections between people.
You take on a new style of clothing, in part, so that you escape from the lack of thought about your clothing and the body which the clothes cover. (If I'm right about this, there is an obvious reason why teenagers would be more involved with such changes of style. That is, they are in the process of discovering their adult bodies.)
You take on a new hairstyle, in part, in order to have new thoughts about your body and, thus, about yourself. Or it could just be that you are older and male and any earlier hairstyle is now impossible. Either way, style is both a discovery and an expression of new thoughts about yourself.
Equally, we are much aware that other people exist and will look at us. Generally speaking, other people don't see much of our bodies. (There are exceptions worth some other essay.) They do see our clothes, our hair, quite likely they way we walk, all of which are subjects of style. The reality is that they notice a lot less than we think, but they are more likely to notice if any of these change. At a minimum, one person's changing style increases the notice given to that person by other people.
Changing styles can be a way of exploring the thoughts others have about you. In actual reality it can be difficult to know what other people really think. They may be too polite to say. They may not care enough to say. They may not even know what they think.
In lieu of direct statements, you can evoke an indirect response which will give you some information about other people's thoughts about you. If you change your clothes and all your friends begin to shy away from you, that tells you something about the relationship between you and your friends. If you change you hair and casual acquaintances start wanting to be close to you, that tells you something. (The exaggerated view of guys that a change in style will instantly attract swarms of girls is probably not actual reality. The effect I'm thinking of is somewhat more subtle.)
It is my contention that such changes and responses is not only factual but also useful. I suggest that changing styles have the salutary effect of increasing the amount of personal and social information available to the person who changes, and that this increase in information is beneficial and an underlying reason why styles continually change.