For LCDs refreshing at 24Hz can be technically bad. They cannot hold the liquid crystal in one orientation long term so you get apparent flicker as the pixels drift and then snap back at the next refresh. Of course, you could use 48Hz with frame doubling because most LCDs don't drift much in 21ms but even that could be too slow for a particular panel. It is also more expensive to support more refresh rates because you need to tune the refresh electronics for each refresh rate, requiring a better controller and more work up front. Not much more expensive today but you do have to spend something to support each refresh rate.
That said, I suspect most TVs don't that support 50Hz today could but don't as a simple region locking mechanism.