The "Ralph Lauren" brand is interesting. Everyone from urban youths (undoubtedly the target of the OP) to Ivy league preppies (RL polos with small horses are still a staple of the college set) to regular middle class folk (khakis, button down shirts or sweaters with polo horse, etc) to New York socialites (Black and Blue Label, RL "collection" items, etc) wear Ralph Lauren, and the brand means something positive to each demographic. Other brands have tried this and failed miserably (Tommy Hilfiger being the biggest example). Yet I also find that there is a lot of backlash to the brand (even on this site occasionally) which is odd when people go wild over stuff like J Crew every season over on SW&D because the brand is so widespread.
I think the environment of the retail stores has a lot to do with ; the stores have basically remained the same even as RL has branched out, and they set the tone for the entire company. At the same time, even on the high end, the brand isnt seen as a "fashion" brand like Louis Vuitton, Gucci, Tom Ford, or whatever; it lacks fashion forwardness, which is actually a positive for a lot of the buyers of the various lines (you could argue RRL is in a way fashion forward, but not in a runway type of way). On the "low end," the stuff sold at department stores still looks better than comparable items and can be had at reasonable prices.
Finally, I think RL stuff can be described as "affordable luxury" in all of the different segments he operates in. If you are a kid who wants a nice polo shirt, you can get one for Macy's on sale for $50 bucks. Your Nike shoes or whatever may cost $100 bucks, so the Polo isn't that expensive. If you are a college sorority girl and you want a cable knit sweater, you can get one for $200 bucks or something on sale, and it will be well made; i'm sure some other brand (whatever college girls wear nowadays) could cost a lot more. You can spend money on other stuff. If you are a dude who works in an office in Manhattan, you can buy some really nice brown cordovan wingtips to go with your suits (and maybe jeans) for $400 bucks pre tax on sale. The next level of shoes (Edward Green, Lobb, whatever) cost $1000 or more, All the more money for polo shirts for the weekend, RRL denim, whatever else you need (this basically describes me).
Honestly it may just come down to the fact that everyone likes and respects Mr Lauren himself and what he claims to represent, and they don't mind associating themselves with the brand regardless of who else is wearing it, particularly given he provides so many types of looks.