Because they are masochists
Because they have been Christians and seen the light
Because they have been Muslims or Jewish and haven't seen any light
Because they are historians
Because they are ABers and seeking to understand/discover means to take the Theos down a few pegs.
Because they want to waste their time and lives.
Because they want to end their lives.
Bless you, my sinner, yes the world is flat and the Pope is a Catholic - though he could have Cornoavirus. Evidence:
https://www.thetablet.co.uk/UserFiles/images/news/20200227T0752-34491-CNS-POPE-CLERGY-COLD.jpg and the Vat aren't denying that he has been tested.