Of course it is prone to stereotypes, but sometimes having a filter is worth it. For example, if I am at a party, and I see a number of people, one who looks like someone who'd have my interests (a chemistry t-shirt or something video game related) and other people dressed in ways I associate with shallow, vain people (like if you have a purse that cost 500+ dollars), I am going to decide based on how they look who I think I might be more interested in chatting with. Now, I probably won't consciously think this person is bad or whatever, but I will probably discern that her life priorities are different than mine. Maybe I'll be wrong and maybe my initial opinion will be totally defied, but because you don't have the luxury to chat with 100 people individually, you make snap judgments and act on them.