As my cultural symbiology bibliography indicates there is some understanding of cultural symbiology out there. Dennett, Blackmore, Gontier - and so on - but most students of cultural evolution within academia just don't seem to get it. There's talk of "coevolution" - but if you look deeper, this is lip service, most of the people involved really don't understand symbiology. The terms 'parasite' and 'virus' are seldom mentioned. Epidemiological models of cultural transmission are systematically neglected - and so on.
To be clear, symbiology is an important foundation of the theory of cultural evolution. If you don't see culture as composed of cultural symbionts coevolving with human hosts, you don't really understand the topic. Without symbiology there's no way to properly understand cultural evolution. So: what are the academics doing? Why don't they understand?
One clear factor is cultural evolution's scientific lag. Symbiology proved hard for ordinary evolutionary biologists to understand. It wasn't until the 1960s-1980s that the implications began to sink in. These days we know from gene sequencing that the human genome is at least 8% virus. Symnbiology has proven itself to be a very significant evolutionary phenomenon. However, understanding of cultural evolution lags behind understanding of organic evolution. As a result, cultural evolution in academia is stuck back somewhere before the 1960s - back when symbiology was not properly understood.
Another factor may be that symbiology itself was a slow starter. Even in the 1980s understanding of symbiology grew slowly. Its main popularizer was Lynn Margulis - and Lynn was an idiosyncratic individual who seemed to have difficulty expressing herself clearly. She promoted symbiology, which helped it to grow - but no doubt some people didn't get the message because of the medium.
I think another factor is balkanization. Many academics are specialists. Cultural symbiology requires understanding of topics which have historically been widely separated - cultural anthropology and symbiology. This understanding hasn't been properly combined in a sufficiently large number of individuals for it to become widely known.
Another factor may be founder effects. The modern theory of cultural evolution was pioneered by a few individuals. By chance, they lacked the required memes, and didn't have the predisposition to acquire them. The modern theory has radiated from them. Under this model, the problem was bad luck, sampling effects and then magnification.
Memetics pioneered cultural symbiology. It was prominently there from the beginning - in the writings of Cloak (1975) and Dawkins (1976). It is frustrating to see the current level of ignorance in academia surrounding this topic. People are ignorant of the topic only to the extent to which they neglect the memetics literature.