Answer:
A one-person show has the advantage of not having to deal and harmonize with several people, so only one person stars and is on display, which prevents competition among actors and hurting other people's egos. Besides, one-show productions tend to have a lower budget, and if the protagonist also produces the show, he has the freedom to manage it at his or her pleasure.
On the other hand, the actor-producer is responsible for the losses and debts, and has to deal with the complete management and media attention of the show.