Reason is simple, very few people love programming and even fewer love to keep learning to stay up-to-date with new technologies. Its simply hard if you are not much interested in doing programming and were in the profession to get a nice job because everyone else was jumping on the bandwagon while you were in college. It is also possible to lose love for programming after initial interest fades away. It has happened to me multiple times. The only reason I stayed as programmer is because I hate management even more.