Not every wrestler gets to challenge for the big belt. The card is pyramid shaped for a reason, but that just means there's room in the rest of the card for everyone.
At present, it's more or less the same six men in rotation, getting TV time and storylines over and over again. Now, not everyone gets to be Daniel Bryan (hey, it looks like even Daniel Bryan doesn't get to be Daniel Bryan), or have their Cinderella story propel them to the main event.
Many wrestling fans love Heath Slater's work but are still well aware of the limitations of the performer: he's probably upper midcard at best, even if they give him a ball to run with. Equally, Zack Ryder was horribly treated by WWE, but not many people would suggest that he deserved to be pushed to the moon for having a successful Youtube show. However, not being buried would be a start.
The point is that on a three hour show, with a two hour show later in the week, there's enough television time for everyone, and there's no justifiable reason for talented performers to be signed, invested in, given positions in the company, and then told that there are no suitable storylines for them, or no television time available.
The following ten men were released by WWE before their worth to the company could be properly realised. In some cases, these men represented some significant investment of time and money, which was abandoned when they received their marching orders. Nevertheless, they had greater potential than the WWE chose to see in them or exploit.