Here's a touchy subject if there ever was one—determining whether or not a driver "deserves" to race at the Sprint Cup level or not. It's a subjective thing, one that may or may not involve accidentally insulting folks' livelihoods without comprehending the backstories they had to overcome to make it to the top.
Let's be real here: The majority of these drivers earned their shot to be competitive at NASCAR's national level. In the right equipment, and at the right level, just about every one of them could be successful, contending for race wins or championships. Many of them have.
In fact, a lot of these drivers have struggled in Cup primarily because they weren't ready for it when they debuted. Many of them had rides with prestigious teams that they simply couldn't pass up, but as a result, they did long-term damage to their careers by failing to perform. Unreasonable expectations don't help, but neither does walking into the wrong situation.
That being said, with an incredibly talented crop of young drivers on the way up—from Roush Fenway Racing's Trevor Bayne, to the Dillon brothers at Richard Childress Racing, to the entire Turner Motorsports driver lineup—it shouldn't be a shock if some of these drivers are out of Cup completely within the next couple of years: