This may seem like a funny question, but I've seen so many ground beetles upside down on the floor and wondered why they've never evolved the ability to get back up. Wouldn't something like this drastically increase their survivability?
By "floor", I'm assuming you mean a smooth floor like that inside a house or building. I imagine that these beetles are actually quite good at flipping themselves over when they have something to grab onto -- e.g. a blade of grass, a fallen leaf, etc. The detritus-free environment that is the modern indoor floor (or smooth path, or paved road) is not part of the natural niche of these organisms, and encountering such surfaces was uncommon in their evolutionary history. Rare encounters are weak selective forces.
Normally, if a healthy bug is knocked onto its back, it can use its legs to rock on its sides until it rights itself. If, however, the bug can't roll back onto its abdomen because it has become too weak or because its nervous system isn't functioning properly, it remains stuck on its back.
An injury, a compromised nervous system due to pesticides or a lack of food or water can also reduce a bug's ability to right itself. Or the bug could simply be at the end of its lifespan and its strength and coordination abilities are declining.