That's because Kishimoto didn't plan anything for the Uzumaki's from the start. The Uchiha always had the Sharingan and the Clan Massacre to work off of.
From how I understand it. Until the Meiji Era only Noble Families had Last names the Names of their Clan. In fact, it was so important when someone had a clan name when someone introduced themselves they say their clan's names first before their own. In other words. Uzumaki, Naruto instead of Naruto Uzumaki. This also gave the Japanese the mindset that the Clan/Group was more important than the individual. Now, that said, while the individual was suppose to serve the clan first, the clan was also suppose to take care of their members. That also led to Japan's problems with orphans. Since, the clans are suppose to take care of the children, and adoptions are suppose to be bring in people that will benefit the clan; not useless non-clan children that would only be a drain on the clan's resources.
So, Naruto was a member of the Uzumaki clan. He was an orphan; so, his parents must be dead. But he was also all alone; which, means his clan must all be dead as well, else they would have been taking care of him. The fourth was his father but since people don't immediately realize that was the case. Must mean he was from a lesser status clan that marry into a higher status clan.
So, the Uzumaki name originally served two purposes one to give Naruto an easy theme name to remember like Hanuro, Sakura and Hatake, Kakashi, as well as hide the fact that the fourth was his father. His mother didn't exist in Kishimoto's mind beyond that until his wife wanted her to appear. Since, it was to please her, he based Kushina off her, and since he was doing the same to Sakura by that point, and/or Sakura is his type; she behaved a lot like Sakura.
Later on, beyond just pleasing his wife, he expanded upon the Uzumaki clan because he wanted to keep paralleling Naruto and Sasuke and trying to justify why people should care/what was so important about Naruto was chasing after Sasuke. Originally, he was fine with just paralleling Naruto to The First and Sasuke to Madara. But it went further and further until it hit the clans. Now Minato could have been a Senju but that meant that Naruto was a somewhat Senju. The founding clan of the village and in theory Tsunade's clan. Which leads to questions of why Tsunade or another Senju wasn't taking care of Naruto and what happened to them anyway? So, to avoid that meant that the Uzumaki had to be suddenly the clan tied to the Uchiha. And so now must be important.
Again originally the Uzumaki was just a cover to hide Naruto was the fourth's son and weren't that important. All the importance came from Minato from his appearance, his actions, and the powers he inherited. But, now the Uzumaki had to be important. So he looked at what Naruto and Kushina had and what wasn't explained by coming from Minato. So, the Uzumaki became a clan of red heads, who were master sealers (originally from Minato,) and with great vitality to the point of have both large chakra reserves and a healing factor (things the originally came from Kurama.)
Edited by Bail o' Lies, 12 November 2021 - 01:27 PM.