Quote: "I know you're talking about Dragonball Z, but thats so true for Dark Basic as well"
heheh I still feel the effect of that sudden retina desaturation. But DB was perfect back then.
Quote: "why? how did it begin?"
In the beginning, the cartoons did not look very good, the story seemed to be lost, it was excessively distorted. It looked like the creators were forcing something.
Adult themes were used to attract some attention. In a beautiful day, with no apparent reason, Bulma started to use a black rabbit costume. There were many scenes that had nothing to do with the story but were efficient attention catchers.
The amount of adult content got reduced to almost null as soon as the anime became independent of them. But, in my opinion, DB never needed that.