Factories and companies are pleased that so many people “gamble” because ______.

C
根据文中Factories and companies that need money are pleased that so many people are willing to “gamble”.即“需要钱的公司或者工厂很高兴看到能有那么多人加入这场‘赌博…’”因为这些公司需要股民的钱来做生意，因此C选项正确。