This is because until the late 1990s people were not allowed to speak their native language; and, in fact, Spanish was the only language taught in schools.
دلیل این است که تا اواخر 1990s مردم اجازه نداشتند به زبان مادری خود صحبت می کنند؛ و، در واقع، اسپانیایی تنها زبان در مدارس تدریس می شد.