No, they probably can't find the 'sponsored' text, but they are also conditioned to know that the stuff at the top and the stuff on the side is probably ads, because every friggin website on the internet has ads in those locations.
Sometimes I get the result I am looking for in the top ad, why wouldn't I click on it? It's mostly companies which buy ads for their own brand names, for example if I search for Nike all the ads are from the official store or website.
On mobile the first ad almost fills the whole screen so I'm not going to waste time scrolling further.
Hell I've accidentally clicked the sponsored results on Amazon, because my adblocker didn't remove them and it took me a minute to realize Amazon had started doing that.