When the liberals critique issues in society, it tends to come from a point of moralizing. This is especially the case in social issues like sex work or the decriminalization of recreational drugs. They will say that the people who have to make a living either doing sex work or selling drugs “have no dignity” or “Should have done something differently.” While I can understand why a rightist would think such a thing, this seems to ignore the reality of America being a third world country with no opportunities, human rights, or the potential for anyone to do anything productive with their lives. I have to give a side eye to these people who like to give others the impression that they are so progressive and advanced in their political analysis but then participate in blaming the people in poverty for their own survival.
In a society where not a single person is able and willing to help those who need it, people still find it appropriate to look down on those who are not fortunate, if they are not engaging in charity or other activities to help them while not wanting to address the uncomfortable material conditions that cause them to need help in the first place. Helping the poor while avoiding asking why they are poor, seems to be a form of virtue signaling and self-satisfaction, although I do think the intentions of the people involved are mostly benevolent.
The best answer to why liberals are so judgemental I can come up with, is because the culture of The United States is formed around survival in a capitalistic society. So the desire to hustle, emulate wealthy people and the focus on responsibility of every person for their life situation tends to reflect that. This has even influenced minority communities and created respectability politics and other movements to assimilate both culturally and politically into the United States. Influence from capitalist realism has even created ideologies that are freaks of nature such as conservatism in minority communities that would paradoxically be the targets of social conservatism in this society, which are obviously created in an attempt by these people to obtain a similar quality of life as white people. In such a society, it does not matter whether a person did not have a choice to be poor or not, because they cannot be your customer or provide you with any kind of economic help if they are not in an economic position to do so. Even marginalized people such as Trans people or those with disabilities, are looked down upon for their likelihood of having issues with employment or being self-sufficient in society.
The reason liberals are so judgemental of the proletariat, even when some may be classified as a member of the proletariat themselves, is because they have internalized the constructs of capitalist society as being inherent and not as man-made systems that are created artificially by humans, and because association with people who are so marginalized limits the chances of their own survival in society (at least on a subconscious level). This creates a kind of resentment to such people which stems from primitive evolutionary psychology. Because many people living under capitalism are more likely to succeed if they accept it, this reinforces the societal attitudes that promote darwinistic and reactionary ideologies. The saying “Go woke go broke” reflects this, and because liberalism is already a reactionary ideology pretending to be progressive on social issues, the people subscribing to such an ideology are unlikely to ever break free from the thought patterns that cause them to think that way.
Because they have to justify class division to themselves and others.