Of course the audience also figures in. Scriptwriters try to give the people what they want, and I'd imagine more people are interested in humanized AI with emotions. Spock is a cult-figure, but Shatner's had a more successful career.
I think the simplest explanation is that movie consumers like stories involving emotion, whether it's humanized cars (Herbie the Love Bug), cleaning robots (Wall-e), antz or AI's.
@phil: Agree. Bad guys are portrayed as emotionless or evil tools, good guys get humanized. Question is why economists, who generally dedicate themselves to improving the lives of strangers, are demonized. We're the Mother Theresas of the academy :)