Because he is only talking about categories that can contribute to the system. [Scammers] do not. In so far as the system and the diagram is concerned, [scammers] are to be thwarted and their harmful effects mitigated. A lot of the work done in crypto is security which is entirely about thwarting [scammers]. As an example, The original bitcoin paper on double-spending problem is devoted to securing against a particular type of scam.

Speculators fall in a gray area and need to be dealt with on a case-by-case basis. many of them are straight up scams, Some are legit, and the rest are in between. Stratton Oakmont was a scam. Does that mean your index-fund is also one? Or the stock market and financial system as a whole?