I didn't write this blog post, but I couldn't possibly say it any better than this post from 'Play to Learn Preschool" does. It is full of information regarding why preschoolers (and kindergartners, for that matter) should learn to print their capital letters first. It just makes developmental sense! Read more about it here: http://www.playtolearnpreschool.us/2015/08/learning-to-write.html
Enjoy!