Apple XR matte finish colour chipped off.

I am using Apple iphone xr for the past 5 months and recently the matte black colour on the side of the volume button is chipped off without any accidental drop.Is this not the manufacturing defect with how low quality aluminium it had been made?So why apple is not putting this under warranty?

i did’t spend 50k for a phone whose matte finish gets chipped off.