They pick a person to drive magazine sales. The more provocative selection, the higher sales. I really couldn't care less, since I don't even read Time
These days, I don't read TIME either. The quality of the writing (and research) deteriorated over the last two decades.
However, initially, the idea was a very good one - an attempt to identity the people, or individuals, who had had a significant impact on the world (for good or ill) over the previous year.
Most US presidents have made the cut since the tradition was introduced - only one has not.