Malte, I agree that there is an expectation to receive a benefit. Incentives certainly attract donations, perhaps more money from people who want a particular perk.
With me saying that it’s the donation that truly matters, this viewpoint of mine would be severely tested if a project that I am very passionate about and would donate thousands (I can dream!) but the perk for thousands of dollars/euros/pounds came with an invite to recording sessions in the US that I couldn’t possibly attend!