My guess is that these signatures transform the chessboard into an official artifact of chess history, that will have more value for at least some collectors, and can be later displayed in expositions ("Chess in Kazakhstan") or auctioned for charities.
Expect one day to read the headline: "The chessboard were Ding scored his famous comeback win in the 6th game of the 2023 World Chess Championship has just been sold for $XXXXX to an anonymous fan. The money will be used for the Kazakhstan's Development Program of YYYY..."
The chess table that Karpov and Kasparov used in the second half of their 1990's World Chess Championship is still on display in Lyon Olympique Echecs chess club and it gives a very nice amosphere to the playing room.