I always thought Tarkenton scrambled mostly to get a chance to throw the ball. I don't remember him trying to run as much as not getting sacked.
Remember in those days there were none of the "pink tutu's" rule about tackling QBs as there are now. If you were on the field you could get blasted anytime and double that if you tried to run.
And the not winning any SBs those teams survived a lot because of him and no matter what they say now about Minnesota's Purple Gang, they weren't as good as our guys were earlier this year. And teams ran more "down the field" offenses in the passing game. If you couldn't give your QB time to throw he was dead if he couldn't scramble.
envision Dick Butkus tackling a scrambling Fran Tarkenton......