Legends like Jim Murray at the 'Los Angeles Times' and Shirley Povich at the 'Washington Post' were the most beloved guys at their papers. They'd write a cherished column for 30 years, and that was it. There was nothing else to do, no higher job to attain.
As anyone who has read 'Sports Illustrated's Steve Rushin knows, it's quite possible to write an unreadable column without being a TV pundit. But if you want to be a consistently good columnist, you can't be on television.