Earlier quoted context omitted.
Because it’s unnecessary and brings outside influences that could corrupt it’s stated goals
You can be corrupt without having a lot of money. There are countless examples of such. I applaud the their moves. The more money they have, the more likely they are to exist in perpetuity. Needlessly limiting their revenue isn’t going to solve anything.
I think the opposite is true. Consider examples like broke lottery winners, the resource curse [1], and the long history of startups getting lots of money and then cratering, from Webvan to WeWork.
With Wikipedia in particular, I'm concerned that the more money there is, the more attractive it is to people who want to be near large streams of money for various reasons, including living large and diverting money to their own friends, pet projects, and grand visions. I'm also concerned that even if they are able to avoid those people entirely, large budgets pose other risks, including inflexibility in downturns, which I think increase the odds of a setback turning into a full collapse.
Corruption, like cancer, is statistically inevitable for organizations. The only question is whether they have the right mechanisms to detect and exercise the tumors when they're small. But the scrappier Wikipedia stays, the less we have to worry about that.