Even the wealthy can't escape their craving for attention, and charity is their most "cost-effective" tool. After all, a donation leads to endless media exposure, and their public image skyrockets. On the other hand, it is precisely because of these celebrity stunts that the public’s focus is drawn to distant social issues.
It is not all charity that is public. Only very few. Most of them go unnoticed by the public and even unannounced. The wealthy already are popular their charity doesn't make them more popular. Some of the charity works that they are involved in are just critical needs in the society that out of their generousity they decided to solve. Besides morally giving to charity feels good and should be practiced by everyone who has nothing against it.
Exactly what I said millions of dollars are given anonymously to many charities around the world every year.