Probably because the only Uzumaki we knew was Naruto in the entirety of part 1.
The reveal of the clan was also pretty sudden and made characters we've already known relatives. And yet they didn't knew that.
It also was strange to us at first because no one told Naruto what the Uzumaki clan is. It's stuff like this that made it an "asspull" for some people.
I agree. I mean, even if Hiruzen and the higher ups wanted to deny Naruto his heritage, it still wouldn't make sense that he screamed his name out to Haku, Zabuza, Orochimaru, Akatsuk members, etc etc, and no one, not a single person made any remarks about the Uzumaki clan, the clan that was supposedly feared so much that nations banded together to destroy them. Kushina said that the clan was a bit savage, that makes it even worse, guys like Zabuza, Kisame, Orochimaru are like thee most savage guys in the series and Zabuza even kept a special, personalized bingo book where he recorded information and this guy still didn't know nutn bwt the Uzumaki? Yeah I agree, asspull no jutsu.