Because there is a U.S. Patent on the use of LEDs for aquarium lighting.
PFO was a big name in the industry and the first to make an LED fixture for aquarium use. Then they were sued for patent infringement and went bankrupt from the legal fees.
Most of the LED stuff u see now is imported from china, where they don't care about patents, etc.
After seeing what happened to PFO, I suspect the "Major Players" don't feel the profit margin will be worth the effort after paying royalties or fighting the patent holder in court.
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