Chess at the window table

Text 1: Café Rosa, by Lorenzo Hale

An original novel extract.

Every Wednesday the two old men played chess at the window table of Café Rosa, and every Wednesday the game took the whole afternoon. Mr Abbas played white and moved quickly, tapping the clock as if he were swatting a fly. Mr Dunne played black and moved hardly at all. He would stare at the board for twenty minutes, his coffee going cold beside his elbow, while Mr Abbas read the paper and sighed. Luca, who waited tables on Wednesdays, had learned never to touch that table, not even to take away the empty cups. Once, in his first week, he had picked up a saucer and nudged a bishop off its square, and both men had looked at him with such horror that he had apologised for ten minutes. Now he simply brought fresh coffee and set it down on the windowsill, well away from the board.

Explain why Luca never clears the cups from the chess players’ table.