To be fair, Nintendo 3DS shells aren’t exactly very high quality either.
I have an original Majora n3DS XL. After a few months, the golden paint started disappearing around the borders, where my palm/fingers would rest.
To their credit, I could get a free replacement shell (with the right colour and pattern) from customer service when I asked about it. But after this I just resorted to using a clear rubber outer case to keep the paint from rubbing off again.