It's hard to say... I would say it is simply a preference. For instance, it is absolutely fine to use 个 to measure an idea, or a bulb. It is acceptable, but not so good, to use 个 to measure a TV set, a car, a people or a film. Instead, 台,辆,位,部 should be used respectively. Normally, people expect very young children use 个 to measure these objects. And it is unacceptable to use 个 to measure a horse, a fish, a book, or a piece of cloud.