Speaking at Hockenheim, which as yet does not have a deal to host a grand prix next year, described the disappearance of historic tracks as "wrong".
Losing Monza, which has struggled in recent years to strike a deal with the commercial rights holder, would be "stupid".
"I know the people here [at Hockenheim] very well," he said.
"They're putting a lot of effort and passion and they're very keen on staying, on having the grand prix here. It's a great show but I don't think they make any money.
"I think they lost money last year, and thanks to Mercedes [which took on title sponsorship of the event for 2019] they were able to have the grand prix again. So I don't know about the negotiations for next year and how much more money they would need or not.
"The problem is that Germany isn't keen to pay anything, so you need people from outside, investors. The government isn't happy to support, unlike in the Netherlands [which is supporting the return of the Dutch Grand Prix] and other places that we go.
"I think the way they [F1] string their business is based on how much people pay and then you get a grand prix. It's important that we don't lose certain grands prix, it's irrelevant what they pay.
"F1 without Monza would be stupid. Losing big countries with a lot of history like Germany or Spain is wrong."
Vettel pointed out that many races which joined the calendar during F1's eastward expansion under Bernie Ecclestone are sparsely attended.
"People always want to make money and profit so it doesn't help if [some] tracks pay less than others," he said.
"It's important to bring the sport where there's passion for the sport - so keep countries like Germany in the calendar, the UK and all those iconic places. That would be my take on it.
"It's more fun as well for us to drive in front of a lot of people rather than empty grandstands, even if they're all equipped with new seats - useless when there's nobody sitting on them."