Have you noticed how intense the fights get over whether, say, homosexuality is a 'choice' or whether it's an inborn characteristic can get? Or the spats over whether some unenviable statistic about the current status of blacks or women or others is due to historical wrongs?
Why? Because even total assholes find it hard to continue beating up on people for things they have absolutely no control over forever. The pleasure of moral rightness just doesn't last. People who 'chose' to be whatever depraved subhumans we are talking about today, though, nothing is sweeter than punishing the wicked for their crimes.
For some reason, and against apparent logic (even economists who don't start laughing uncontrollably when you say 'trickle-down economics' tend to concede that some amount of unemployment is 'structural') we've concluded that people choose to be poor because... um... government cheese and laziness are totally an attractive lifestyle or something.
This makes minimal sense; but it classifies the poor as sinners rather than victims, so the open season continues (in this vein, you may notice that even die-hard haters-of-the-poor will have a largely ad-hoc 'virtuous poor' category, who are seen as victims for some reason or other. This group tends to be a lot smaller than the set of poor people, so it isn't very socially useful; but it allows a comparison of how people, even a single person treat 'poor as victims' vs. 'poor as morally defective parasites' under controlled conditions, so it's useful for study purposes.