There are many players who take time to develop and find their place in the NFL. A few examples would be Clay (who few thought could be a starter), Jones, Clemons, and even Yeatman who we are still trying to develop. From last year, there was Dallas, Taylor, and Sims, and let's not forget Soliai who was a bust in his first two seasons.
There are many more throughout the NFL, and the bottom line is that coaches have seen something in these players we have not, which they believe there is reason to keep them. Some will work out, others will not. Egnew improved in his second year, and who knows what happens this year?
I go back to our "microwave society" looking for players to be good instantly, and that does not work in the NFL.