Respectfully disagree.
Since the 60's (and one could argue, even long before that), watches are 1) fashion, and 2) male wealth-signaling fashion. That's it. Nothing more. And for males who subscribe to this wealth-signaling cult, they know from a long way away what watch brand is on that guy's wrist.
Okay, today's brands signal maybe a little differently than just wealth. Casio G-Shock watches aren't substantially different than their non-G-Shock counterparts in any significant way, but they cost way more. The G-Shock brand signals... I dunno, sportsy-ness? Maybe it is closer to a pure fashion brand here.
I think we've been in "The Brand Age" since the advent of advertising. There are plenty of products that have virtually no differentiation besides brand, and there (almost) always has been.