There are lots of problems with that approach, unfortunately:
Returning means you need to repack and re-ship the item. Sometimes they cover the shipping cost but not always
Sometimes the counterfeit item only becomes evident after the return window has expired, like buying a wireless adapter for game controllers that breaks in 2 months. (It turns out one of the earliest rampant counterfeit issues on Amazon was people selling knockoff USB adapters for XBox controllers, oddly enough). At that point you can't return, all you can do is leave a nasty review for the product you bought From Amazon.
Some counterfeits are basically indistinguishable from the real product unless you're an expert. If you buy some vitamins or Tylenol off amazon, do you really have the resources and expertise to identify whether they're fakes or tainted or a batch that failed to pass quality control? So now you have to convince Amazon to take this thing back.
In the end at this point Amazon knows very well how much counterfeiting is happening on their platform and they aren't taking enough effort to stop it. It can't all lie on the individual customer to spot and combat counterfeits, they aren't able to do it.
Anecdotal but I learned that some DJI drone props I bought were counterfeit about 7 months after buying them and after many drone crashes. I explained the issue to Amazon and after a couple of questions, they gave me a full refund. It was only 15$ and probably not even worth my time but it never hurts to ask.
Returning means you need to repack and re-ship the item. Sometimes they cover the shipping cost but not always
Sometimes the counterfeit item only becomes evident after the return window has expired, like buying a wireless adapter for game controllers that breaks in 2 months. (It turns out one of the earliest rampant counterfeit issues on Amazon was people selling knockoff USB adapters for XBox controllers, oddly enough). At that point you can't return, all you can do is leave a nasty review for the product you bought From Amazon.
Some counterfeits are basically indistinguishable from the real product unless you're an expert. If you buy some vitamins or Tylenol off amazon, do you really have the resources and expertise to identify whether they're fakes or tainted or a batch that failed to pass quality control? So now you have to convince Amazon to take this thing back.
In the end at this point Amazon knows very well how much counterfeiting is happening on their platform and they aren't taking enough effort to stop it. It can't all lie on the individual customer to spot and combat counterfeits, they aren't able to do it.