The Z fighters weren't recognized during the Cell games because they had never had extensive media coverage done on them before.
The Tenkaichi Budokai was never filmed, but I'm sure that some people who attended might have recognized the uniforms and hairstyles (or lack thereof), but that wasn't really a huge group of people.
It was later revealed that the announcer had barely recognized Goku and Piccolo. At that time, Mr. Satan was the majority winner of all the Budokai(s) thereafter. He was basically the Mayweather of the time. Totally undefeated in the ring, the common people of the world assumed he was the strongest.
As you can see, the anime makes a lot more inconsistencies than the manga. In the manga, Goku had never been caught on camera anywhere before the Cell games. That whole bit of Goku being given the key to the world after defeating Demon King Piccolo didn't happen in the manga. The King actually took off and left Goku, a child, to fight Piccolo alone. Bulma and co. showed up later after Goku had already left called the media, and told them that the world was saved by the forces of good.
So the aside from the two second place fights and one first place fight at the Budokai Tenkaichi, Goku had not been seen by the entire world before. He had only a few martial arts fans before the tournament became as mainstream as it eventually became. How can you recognize someone you've never really seen, right? Vegeta had appeared on camera once during the Saiyan Saga, and the same for some of our heroes, but only very briefly. Gohan's appearance changed dramatically. Trunks was from the future so nobody recognized him. Krillin should have been recognized because he didn't grow much from child to adult.
That's probably the best answer anyone can give. I saw some other posts that gave really good answers and you shot them down. I don't see why. It's a cartoon. I don't know what you expect.
Plus, I think it would be better to ask: Why weren't the Z Fighters recognized from the Cell games during the tournament prior to the Buu Saga?
To me, that's a much better question, because they had actually been seen on TV at that point. Plus, there were little mascot people doing shows at the tournament, who strongly resembled all the Z Fighters. You will be made to think that someone would have put two and two together by then. However, it's completely understandable for anyone who holds the manga in higher regard than the anime.