Because all blank lines are not made interactive in a form, the problem occurs when I want to modify the source file, I would have to recreate all the fields that are not automatically converted into a form.
Converting a PDF to an interactive form is not a one-click process, and as you've seen, it does not necessarily find all form fields, or, what it finds may not acutally be a for field. I rarely use this function (and I've worked on pretty large forms). When I use it, it's just a way to cut down on the number of fields I need to create, but I pretty much anticipate that I have to touch every single field in the form and adjust it's size or it's position. You will need to do some manual work after the automatic process finishes.