It's brand advertising itself, precisely to give the impression of 'being funded by listeners like you.' NPR has navigated trust far better than average for the media. A quick search shows some 54% trust in them, contrasted against 28% for the media at large.
When media runs non-stop pharmaceutical ads you obviously question their motivation when reporting on pharmaceutical adjacent topics, which are almost invariably neutral to positive. Yet when NPR runs non-stop Walmart articles [1], often in a neutral to positive fashion, most are unaware that they've received millions of dollars from the Waltons.
And FWIW those millions the Waltons have given aren't that much relative to their overall funding, but if you saw an equivalent amount of annual advertising from the Waltons on NPR, you'd certainly be looking at those articles from a different perspective than somebody who's unaware of said funding.