In many countries outside of the US they are. However that hasn't done much to significantly change the working conditions. As long as it remains a 'glamorous' industry that kids aspire to work in, then they know they'll never have trouble hiring new workers. The other aspect is that EA, the mother company, doesn't actually program games. They own IP and publish games. The games are written by various studios with various ties and connections to EA. This means that if a studio gets too troublesome, it is quite easy for EA to cut all dealings with that studio and simply shift its IP from that studio to another studio.
Unions typically protect workers who belong to industries where there are more employees than there is demand.
Programming is a highly-skilled profession that is constantly in demand. We don't need protection because companies compete for the good ones, not the reverse.
Unions by design are democratic institutions, and thus protect the average worker. Good programmers will be hurt by a union more than they will be helped, so the union shops will be stuck with lousy programmers and lose in the market.
