Simplify the following text for a Grade 10 native English-speaking person.
Original: At the time when it was common for the reigning world champion to handpick his challengers , Rubinstein was never given a chance to play Lasker for the world chess championship because he was unable to raise enough money to meet Lasker 's financial demands .
Simplified: Rubinstein was never given a chance to play Lasker for the world chess championship : he was unable to raise enough money to meet Lasker 's financial demands .