Because a lot of CS history are only relevant in a larger/humanities context. In terms of absolute technical value, the historical contributions are not necessarily as valuable. Russell and Whitehead's Principia Mathematica has next to no practical use in modern day software engineering. Their existence helped induce Church and Turing to create modern computer science theory but the discrete mathematics in that book itself holds little value for your average computer scientist outside of being an intellectual exercise.
Another issue is that CS is a branch of applied math that also happens to be extremely profitable. Math operates on much larger timescales than other domains. But business and economics demands immediate attribution. McCulloch and Pitts had their Hebbian neural network almost a century ago. Kleene of the Regex fame designed his neural network in 1951 [0]. These vast timescales are quite normal for advanced mathematics. But in 2010 GPUs became cheap and the obscure theories of the pre-GOFAI age are suddenly immensely profitable. Of course the names and associations would be with their most recent implementors. The ones who actually applied and made it possible, rather than those whom dreamt it up a century ago.