The 2017 edition of the race, pencilled in to be held at Hockenheim, has been marked as subject to confirmation, along with Canada and Brazil on the FIA's provisional calendar.
Attendances have dwindled in Germany since Schumacher retired, and despite Vettel and then Mercedes' success crowd numbers have failed to recover.
This year's Hockenheim race day attracted just 57,000 fans, which although higher than 2014 was still well below the levels required for the circuit to break even, with a full-weekend attendance of 122,000.
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In contrast, Austin reported a record attendance of 269,889 for the three-day United States GP weekend while Mexico reported 339,969 for its recent weekend.
When asked why those two relatively new races are able to draw such big crowds while Germany, with its rich F1 heritage, a reigning world champion team in Mercedes and four drivers on the grid, cannot Wolff said there was no "simple solution".
"If you look at Austin the crowd was great," said Wolff. "What has been organised around it has been great with lots of innovation for the fans.
"We need to look beyond the tip of our nose and how we can activate the fans which we have lost.
"If there was a simple solution we would've found it.
"It's a bit of a hangover in Germany because we have had 10 years of world champions and it has transitioned into other sports.
"Maybe we just need to look at what Mexico and Austin are doing and some other tracks."
Austin's organisers worked hard to attract fans to the venue this year after heavy rain caused havoc with the 2015 event.
The track - which has a 10-year deal to host F1 - cut ticket prices, added a no-flood guarantee and a maximum wait-time guarantee for shuttle services in a bid to appeal to fans.
Organisers also signed Taylor Swift for a concert on Saturday night to attract a younger audience and boost sales.
Wolff admitted it is not easy for GP circuits but suggested the key to success lies in better promotion and an improved all-round experience.
"Well if Taylor Swift is the answer then get Taylor Swift," joked Wolff.
"If Formula 1 is not the only attraction anymore then you need to add other attractions.
"I'm not aware Taylor Swift was in Mexico City and there were full grandstands on the Saturday and a sell out on Sunday.
"There is a lot of advertising and Mexican drivers with narrative created around them.
"It sounds easy but you need to take the right decisions to promote a grand prix."
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