I guess if you've got more money than you know what to do with, and no sense of either taste or value, then these are just the thing to pimp your ride.
The whole idea of bling is pretty distasteful to me, but I can't deny that it gets attention. And for those who have adopted that approach to self-promotion, it may very well turn them into attention whores (assuming they're not that already). While bling may be relatively harmless on cursory inspection, I suspect there is a lot more going on at the Gestalt level. Put another way, it's the Zeitgeist of our time (love them German psych terms) that livin' large, baby, is no longer something to be embarassed about; rather, it's become a categorical imperative.
It's true of most of us that at some point we've uttered the equivalent of "sure, I can tap dance." The implication is that you then go out and learn to tap dance. If you eventually show up and still can't dance, they you deserve what you get, which will likely be the boot. With bling, it's not about earning attention, it's about buying attention. Oddly, the payment isn't even made to those whose attention is desired but to a third party. "Watch me buy stuff" has replaced "sure, I can tap dance."
Much the same thing is going on in the media, which must above all be visually tantalizing even if other types of content are mostly banal, saccharine, or insipid (or combinations of the same). It's tease, tease, tease, but rarely deliver. And we're lapping it up like the dogs we are.