I think it may be because of it's almost neutral characteristic - it's like the beige of the color world. It has been credited with being the new black in fashion trends but of course many colors have been awarded that claim as they fall in and out of favor.
I began to consider how marketing something as just brown can be counter productive to increasing sales for retailers. For example, which sounds more enticing, a 'brown' pillow, or a 'mocha' pillow?
In looking at synonyms in an online dictionary for the color brown, these are the variations I found:
|Shades of Borwn - Flicker Creative Commons|
Cafe au lait
Now whose to say what constitutes chocolate and what makes for cocoa...rather subjective I would say but I think there would be agreement that colors like carmel (caramel) and tan would be more in the middle of the spectrum and cafe au lait and buff on the lighter side.
. And beige? I never considered it in the 'browns' - more in the darker 'whites' but again that seems to show how subjective colors can be.
Are you a brown lover? Let me know in the comments which brown is your favorite.