* He was not famous yet. He was primarily a radio performer and did not achieve widespread television success until the late 1950s and early 1960s.
* Television was still relatively new. While television shows existed in 1955, the industry was not as developed as it is today.
It's possible that Dick Van Dyke may have performed in Atlanta at some point in his career, but there's no record of him starring in a television show there in 1955.