I've wondered that too. The only thing I can think of is, like other people said, the products are cheap. Maybe it's also because it's a big store, easy to get lost in the background, and the atmosphere is lax, maybe because the employees are paid pennies and don't give a damn about enforcing any kind of dress code, so people may bot bother not making it obvious they're low-class or the low-class people feel more comfortable shopping there.