Because they pursue profit margins of x100 or x1000, and Bitcoin plus Ethereum can't provide that return anymore on short or medium term, considering the current level of consolidation they already reached.

I believe people who have already been scammed or exposed to scams have more chances of learning to not fall for further similar schemes in the future. It means investors who are already part of this industry are prone to learn with their own mistakes.

However, there are always newbies starting their journeys in crypto industry all the time, so this public is the most likely one to fall for the scams of the next bullish cycle. That is why we never get rid of scams. There are always new schemes, because there is always new people getting in touch with them for the first time.