> Maybe this kind of behavior is more common in liberal arts?

It isn't. I've worked in a research group that focused in a specific engineering domain, and once I've noticed that my own supervisor published a paper with the results I got from computer simulations and informally shared with him to ask for his input on the findings. Essentially he took my plots, tweaked their appearance by changing color schemes, labels and ranges, and wrote a paper around those plots.

I couldn't do anything about it because in practice the only proof I had were the plots, and the paper was on a subject that was supposedly the advisor's specialty. Furthermore, back then my tenure track depended directly on that man's say. So, even if I had irrefutable proof that he usurped my results to publish his own paper, blowing the whistle on him would end my career.