If you could care less then why don't you
A lot of good points here. Certainly brand loyalty comes into play as well. For example a family where the father say owns that vintage watch the son or daughter may be predisposed to also get a watch of the same brand. Or it may be bought for them as a gift. Thus perpetuating the loyalty to that brand, image vs quality or not. For whatever reason, Rolex seems to have obtained that high level of customer loyalty and people also view it as one of those time pieces that can be passed down for generations. Chalk it up to marketing I suppose.
As for visibility, people who own a particular brand / model will often notice it much more at large then they would any other item. Like redwatch I couldn't care less what people think of what I am wearing. And in fact I have had just as many comments, if not more, wearing other brands than Rolex. I'd say in a lot of cases how a watch appears visually has more to do with the attention it gets rather than the brand. Most people wouldn't even know where to look for the brand markings let alone see them or notice them at more than an arms length away.
At the end of the day I think many if not most or all (around here anyway) wear it because they "like it". Why we "like it" is very difficult to define and would probably take some significant psychological analysis. But there is no denying that at least to some extent it has to do with image. I'm sure faced with the choice of two identical WM9 subs, one with brand marking and one sterile, I would choose the marked one. How about you?