I think is a fair comment. The people involved probably wouldn't give the steam off their coffee to the someone struggling right in front of them.
I don't know why we should assume Redditors are less charitable than people at large when if anything they've demonstrated otherwise.
It's a good venue for charity and people helping others. No one who has spent much time with humans should be shocked that the same people are also sardonic assholes at times.
What do you suggest we do for the people struggling in front of us? Also that is a broad brush you are painting a lot of people with. It's likely that many /r/wallstreetbets users donate to other charities. Americans tend to be quite generous.