Your skin produces melanin as a response. Sun exposure triggers it. Inflammation triggers it. Hormonal changes trigger it. Skin injury triggers it.
In most people, this response is controlled. Melanin is produced, distributed evenly, and everything looks normal.
In people with hyperpigmentation, this response goes into overdrive in specific areas. Your skin produces excess melanin, it clusters together, and you get dark spots, uneven patches, and melasma.
The reason your spots keep coming back after you fade them is simple. You faded the melanin that was already there. But you never stopped the overproduction. So your skin just makes more.
This is the problem that most of the skincare industry refuses to solve. Because solving it means you stop buying their products.