Why do stars use screen names even if they have beautiful real names?
Most of them do it for easy recall.
The late Fernando Poe Jr., for instance, was actually born Ronald Allan Kelley Poe. He had to borrow his brother Andy's real name Fernando Poe Jr. to bank on the popularity of his dad Fernando Poe Sr.
Another example is Sharon Magdayao, who was named after Sharon Cuneta. When she entered showbiz in 1986, she was introduced as Vina Morales, the combined name of Vic Del Rosario and his late wife Mina Aragon. Her screen name was also inspired by Divina Vanessa, the eldest daughter of VIVA's big boss.
When Pia Wurtzbach first joined showbiz, she used the surname Romero, which was, of course, easier to remember.