Vettel is out of contract at the end of the 2020 season and will leave the Scuderia team after a six-year stay, where he has so far amassed 14 race wins.
"I think Sebastian, being a four-time world champion, I wouldn't say he'd want to go to the midfield anymore," Steiner told Sky F1. "If you have a successful career, what you don't want to do is to take too many risks.
"I've got a good relationship with him but I haven't offered him a seat. I think somebody else with a lot deeper pockets than me will do that!"
Steiner was asked if it would be possible for Vettel to come in and help the team with the development of its car, which struggled throughout the 2019 season.
However, Steiner says limited test days going forward would complicate things and also questioned why Vettel would carry out such a role for the American outfit.
"Absolutely it would be fantastic to do this," he said. "But then just getting in a car after six months out of a car and then making a decision would be very difficult.
"And then also what we have got is there will be very, very few test days next year, so it’s very difficult. Testing the 2022 car, the hybrid car we are building for next year to go testing with the bigger wheels , would be fantastic.
"But I think it’s difficult to do these things, just jumping in and getting an opinion about it, and I think he would be reluctant to do that as well, because what does it do for him? Not a lot.
"He’s four-time world champion, drove 15 years in Formula 1 and has done it all and won it all, so why would he do that?"
Bahrain International Circuit - Winter testing