Firstly, not everyone is like that.
Second, It's human instinct to guess the unknown in order to fill one of the biggest human's desire which is "curiosity".
Take the clothes for example. When you see someone with dirty or messy clothes an unknown subject with trail of guesses will shape in your mind.
Maybe he doesn't have financial power to buy new clothes? Maybe he's rich enough but just prefers to go around like that? Maybe he's just a normal guy who lacks personal cares? Maybe recently he's been depressed & avoided self care? Maybe the moment we'd seen them that way they just been involved in a fight, accident etc...
We all make guesses & judge in that way, whether we realize & accept it or not.
The other type of judgement is giving worth & good personality by what people wear, how they look, & where they live.
In simpler language... some people judge others by how much their clothes & houses & places they visit actually cost. I don't have anything to add about those type of people, I only call them unwise, unthinking & materialistic people. I've never been one of them.
But I'd guess that's also one of unstoppable human's instincts. Especially since our lives on earth are moving everyday towards a more currency-based & materialistic system.
And yet there are so many types of people who are fighting against these prejudices, and so many things that can't be bought with money: