Maybe they learned from this guy: http://www.sunnipath.com/resources/Questions/qa00002582.aspx
In the name of Allah, Most Compassionate, Most Merciful,
The blessed Companions of the Messenger of Allah (Allah be pleased with them all) used to explicitly prohibit the playing of chess, and it is obvious that they must have heard this from the Messenger of Allah (Allah bless him & give him peace) himself.
Sayyiduna Ali (Allah be pleased with him) said: ?Chess is the gambling of the non-Arabs?. (al-Bayhaqi in his Shu?ab al-Iman)
Sayyiduna Abu Musa al-Ash?ari (Allah be pleased with him) said: ?Only a sinner plays chess? (ibid).
He was once asked about chess and he replied: ?It is useless (batil) and Allah does not like useless things? (ibid).
Due to the above statements, many scholars including the Hanafi Imams have prohibited the playing of chess.
The great Hanafi jurist, Imam al-Haskafi (Allah have mercy on him) states: ?It is prohibitively disliked (makruh tahriman) to play backgammon and similarly chess?.
Allama Ibn Abidin (Allah have mercy on him) explains:
?The reason why chess and backgammon is prohibitively disliked is that, the one who becomes busy with playing these games is relieved from the stress and hardships of this world (m, meaning it is useless and endless entertainment that only waists time and relieves one from the pressing issues of life) and the pains and difficulties of the hereafter come to him. Therefore, it is unlawful and a grave sin, according to us, to play backgammon and chess. And in permitting it, is assisting Shaytan in his ploys against Islam and Muslims?. (Radd al-Muhtar ala al-Durr al-Mukhtar, 6/394).
Therefore, one should avoid playing chess. The reason is that, playing chess inevitably wastes a lot of time and distracts one from the religious and other worldly obligations. The legal principle (qa`ida fiqhiyya) is that, ?The inevitable is considered actual,? in terms of establishing rulings. [al-ghalibu ka?l mutahaqqaq].
And Allah knows best
Muhammad ibn Adam al-Kawthari
Darul Iftaa, Leicester, UK