My ancestors also had many ways of spelling their names. Sometimes they changed their names completly.

Something about staying one step ahead of the creditors.

In all seriousness, one story I heard about this was that people just did not write their names that much and many people could not read and write at all. As weird as it seems it is possible to forget how to sign your own name if you only do it once every few years and it is the only word you knew how to spell.