A human artist has been trained in the ethics and laws of their craft along with the skills required to make images.
A human artist, asked to clone Starry Night, will ask you what you are doing, and knows where the lines are between "a tribute", "plagiarism", and "outright forgery".
A human artist, asked to do work in the style of another artist, will have a certain respect for the other artist's ownership of their style. This is not a thing that is at all protected by intellectual property law but it is still a thing artists are trained to respect. There are exceptions - drawing just like your boss may be your job, drawing just like a living artist for a couple pieces is a useful way to break down their style and take a few parts of it to influence later work without going over the "style swipe" line, building your own work on the obvious foundation of an influential, dead artist's style is fine - but there are lines professionals will be very reluctant to cross.
For a relatively recent example of what happens if you break these unwritten laws, check out what happened when the American cartoonist Steve Giffen started doing a wholesale style swipe from the Argentinean cartoonist Muñoz: https://en.wikipedia.org/wiki/Keith_Giffen#Controversy
Neural networks know none of these unwritten rules. Neither do the people who are training them. Feed it a bunch of work generated by a living artist and start making a profit off of that? Sure, no problem! Bonus points if your response to them getting pissed off about this is to call them a luddite who is resisting the inevitable, and should throw away a lifetime of passionate training and go get a new job.