Why is fake jewelry bad for healed piercings?

To elaborate more, I’ve had lobe piercings since I was a baby. I exclusively wear fake earrings in those holes and I’ve never had a single issue. My other piercings, though, I only wear titanium or gold, and I understand that if I were to wear fake jewelry it would be bad. Why though? Is there actually a difference? Is it because it’s been so long for my first lobes? Is it the placement? Can anyone explain?