Actually the pairs' short program was introduced in the early 1960s (not sure of the exact year), to serve a similar purpose as the compulsories in the other disciplines, so the singles SP introduced in the 70s was modeled on the pairs'.
Individual pair skaters generally trained as singles skaters also before or during their pairs careers, so they generally did some figures training along the way, but they could easily give it up before senior level once they decided to focus only on pairs and still make it as seniors in that discipline.