I would like to know why some Japanese people's names are usually written in half 漢字 and half 平仮名、e.g. あだち充、長澤まさみ、宮崎あおい、田村ゆかり, etc. But some people's names are usually written in all 漢字, e.g. 杉本彩、田中麗奈、倖田來未、森進一, etc.
Are there any reasons why some people use all 漢字 and some does not?