Even though modern chess playing programs have demonstrated themselves to be as strong (or stronger) than even the best human players for nearly 20 years now (1997 when IBM's Deep Blue defeated the world chess champion Gary Kasparov), why would a game like chess still be considered a valuable research subject in Artificial Intelligence? In other words, what can be gained by continuing to advance AI in areas that have already surpassed human capabilities?
For instance, as recently as November 2017, Google successfully challenged its deep learning technology against one of the world's strongest chess-playing programs.