I don't know about Michelle, but I mill my own flour and cornmeal because it's fresher, tastes better and it's much more nutritious. Besides that, there's a satisfaction in doing it that just isn't there when I buy a container of cornmeal. Flour and meal that was milled weeks or months ago has lost much of it's nutrition, especially the B vitamins, unless it's refrigerated.
Depending on the source, it can be quite a bit cheaper, too.
I have grown some of my own and I bought clean wheat from a feed mill which has lasted a very long time. The popcorn I milled was bought as popcorn from a salvage store. It was old and wouldn't pop well and I didn't want to waste it, so I tried milling it. It was a little powdery because it was slightly overdry, but it tasted good, so I used better corn the next time. I've milled feed corn from gleaning a farmer's field after the harvest and last year I grew a small plot of corn just for that purpose. The seed cost less than $3 and I have enough corn for a couple of year's worth of meal for me (but I'm a one person household).
I have a manual mill that I bought from Lehmans long ago, but I use my Vitamix any more, since my shoulders tense up when I do much of that kind of work any more. I keep my manual grain mill "just in case."