As a psychologist I give it a try.

When writing cursive (if you learned it properly and practise it a lot) you write more or less automatically complete words, with printing you write letters.
If you change from cursive to printing it may that you encountered a word you are not used to write. It is also possible that you concentration is a little bit less when you write printing. Forcing to write letters may help to make sure that what you are writing is what you are supposed to.

Writing in print also leaves less room for errors when reading back

Rob.