Sometimes the immigration officials couldn't understand or spell the 'foreign' names and so they Americanized them. I know of a family who came here from Russia. The father's name was Ralfol Wazanski and the official threw up his hands and said, "You will be 'Raphael.' And so the family is still many years later the 'Raphael' family. Sometimes people Americanized their own names. Around World War I people of German descent often changed the spelling of their names in an effort to disassociate with the enemy. Also people changed their names because of the different meanings of words in English and their homeland. Such as, in Germany a baker might be called 'Backhaus' but over here people tended to associate the word with the 'house out back' that was common to most households years ago.Name changes were easily done in the days before Social Security. I'm afraid there is no 'sole' reason but a different reason in every case. Janice