Thats how music is. Tonic, sub dominant, dominant - sometimes a relative minor.

The song starts and ends in the middle. Soetimes it goes up, sometimes it goes dowm Occasionally theres a sad bit.

Its a bit like objecting to boiling point being hot and freezing point being cold. All triangles having three sides.

Life is a three chord trick. If you can't find what you need with three chords. You're not looking hard enough.

Ewan MacColl wrote a classic song with two chords. Big Bill Broonzy played three chords with more class that Andrew lloyd Webber can get out of a symphony orchestra. (And I bet a musician like Lloyd Webber would agree with me).

Heaven is three chords and the truth. Some people sound shit with twenty chords. Some ethic musicians and modern classicists can bang two dustbin lids together and justify it.

Theres nothing wrong with the basic geometry of music. It can save us all.