Because they know there is a gun pointed at their head. This story is typical. Egypt is considered a moderate Muslim Arab country but it is still a capital offense to convert to Christianity. The only way to be a Christian is to be a visitor or born a Christian. I’ve talked with Muslims in Egypt about this a number of times and they think it is the proper way to keep their country Muslim.
Amid threats from family, Egyptians ex-Muslim receives conversion certificate
Maher al-Gohari, an Egyptian who quietly converted from Islam three decades ago, petitioned a court to change his religion on his ID card from Islam to Christianity. In response, the court asked al-Gohari to provide a conversion certificate, which the Coptic Orthodox Church has issued for the first time. Al-Gohari said last year that since his conversion became public, his younger brother has wanted to kill him: “he’s been waiting for me outside my building with a gun.”