Because that's Apple. Just like how they forces everyone to come in office three days a week. Not every company does that -- some big companies are still quite flexible with full remote work. But this is Apple.
While you are indeed free not to work for Apple (that is what I do!), policies in FAANG companies have significant influence on smaller companies who tend to cargo cult them without much thinking. That is how we end up with leetcode-style interviews, now I'm afraid we all might end up back in office, only even worse one than before where you don't even have assigned table in the open-space.
"If you don't like it, leave!"
Following this advice bolsters bad policies & practices by removing opposition from institutions.
It's noble to stay aboard to fight the good fight. I'm envious of engineers able to take on the risk.