Why does the Olympic Games stipulate that athletes must be amateurs?

1894 The Olympic Charter formulated by the Paris Conference clearly stipulates that only amateur athletes can participate in all kinds of competitions, but fencing can be an exception.

Of course not now. /kloc-required before 0/992. But from Barcelona in 1992, NBA professionals such as Jordan began to join the Olympic Games.

But sports like boxing are not allowed for professional athletes.