Back when baseball was king, the NFL was a niche sport and the NBA wasn't even a gleam in Red Auerbach's eye, the Hot Stove League got American sports fans through the winter.
Boxing and horse racing also jockeyed for status as America's pastimes, but neither prompted animated discussion in the offseason like baseball. The Hot Stove imagery stems from fans gathered around a general store's pot-bellied stove, talking about favorite teams and players.
The imagery was gone by about World War II. America became less rural. In the cities, there were multiple newspapers writing about baseball, and occasional radio reports, and eventually television.