Because Shaq was clearly the dominant player on the team during every single title that Kobe happened to be there for.
While Magic was the dominant player on the team for most of his titles with Kareem.
That's the obvious answer and thread should have ended there.
That being said, Magic joining forces with the league MVP does affect the discussion. One of many reasons while simple ring-counting is stupid as hell.
The idea that straight ring-counting decides the better player didn't even come into the discussion until after MJ. Otherwise Kareem would have been considered a loser until Magic came, rather than already being the consensus greatest player in NBA history. Otherwise people in the 1990s would have been sayingthat MJ didn't surpass Magic until 1998, never surpassed Kareem, and still trails Havlicek. Shaq and Duncan (not to mention Russell) would be universally seen as superior to Wilt and Hakeem, as would Larry Bird, and Jerry West would be a trash loser and not the logo of the damn NBA.
It's not even used consistently now. How many of the ring-counters say that Duncan=Magic=Kobe and they're all superior to Shaq and Hakeem, or that Steph has already surpassed Wilt and Durant could do so this year too? Pretty much the only people who use RINGS!1 are doing it in the context of MJ or Kobe, and even then they're not consistent.