Mecha anime isn’t about mecha. The mecha is a representational shell. It stands in for other things: power and responsibility, usually.
Only during the very early days of mecha, the days of Gigantor and such, was the mecha itself venerated as a god-like being. But Gigantor quickly became a shackle; it was literally a deus ex machina that swooped in at the end of the story to beat the bad guy. It’s hard to tell interesting stories when your hero is a remote god.
So mecha began telling stories about the humans and other people surrounding the mecha.
And as soon as Mobile Suit Gundam ushered in the real robot genre, mecha stories focused on the pilots and their conflicts. Even the super robot genre told stories about people, not giant robots.
It’s part of the appeal of the mecha genre: adolescent protagonists grow and learn about themselves by piloting their mecha. The mecha is a metaphor for the power we get as we grow up.