I'm late to the discussion, but feel compelled to chime in as someone who definitely has a lower half that could use a little "reining in."
I actually own a pair of Spanx pantyhose. I think the last time I wore them was with the dress I wore for one of the inaugural balls, yes, going on 8 years ago. Before that, I wore some Spanx under my wedding dress, 12 years ago. I just don't see bothering with them anymore.
For one thing, my lifestyle is too casual to even warrant many outfits that would require such shapewear. Even my date night outfits don't need it, and frankly, nothing feels less effortlessly sexy than squeezing into a constricting piece of underwear before a hot date!
If I try something on and it is clingy enough to show stuff I don't want visible, I don't buy it. Life is too short to wear uncomfortable things, and there are plenty of other outfits that I find flattering without trying to flatten myself out.
Besides, I wonder, am I the only one who feels like these things squeeze in all the wrong places? They flatten down my already flat butt, and don't so much for my tummy (which doesn't need much help anyway), and do absolutely nothing to minimize my saddlebags. So, not worth it for me. Just my experience. Maybe they're more for tummy control than anything.