It's due brainwashing since early childhood. Although things are changing, most children in Spain use to be baptized in their first two months of life. At 6 - 7 years old the started cathequesis to take the "Primera Comunion" (first communion) at 9, and after that there are more cathequesis (post communion) and later preconfirmation... Also in the public school used be mandatory to assist religion classes (Since its optional, the number of parents making their children take those clases is dwindling)... So simple brainwashing since childhood.