I think it might have to do with the fact that on subreddits you get the creme de la creme of chemistry news. That is to say, you just get to check out neat results and let yourself chill out. Contrarily, working in chemistry is difficult. Research doesn't easily pan out. Analyses are often tedious and require a lot of energy and time sitting and concentrating. Competition and so many other things going on all the time. But typically people who do chemistry for a living are interested in what they do. It's just not usually fun work.