You have to provide the line breaks. My guess is that text on autoshapes was
meant to be a label, not sentences or paragraphs. For the latter, I would
probably create a text box and then give it a fill and line to look like a drawn
autoshape.
The annoying thing is that text in an autoshape WILL wordrwrap but you have to go
through the formatting dialog box each time to set that option. It doesn't hold as
one of the shape defaults, unfortunately.
I suppose the other option is to create a shape, set the wordwrap and other stuff
the way you want it, then copy/paste to get additional copies of it as needed.