It's about space. Wikipedia tells me Copenhagen is 86.20 km [1] and San Jose is 466.109 km [2] but naturally silicon valley is several times larger than San Jose proper. If it was possible to just rent an apartment near where one worked, that wouldn't be an issue but we know how hard that is today.
When where one's work is twenty miles or more from one's living space, one just isn't going to easily bike to work. There could be bike path with wind-tunnel and it still wouldn't be possible [edit: for most, average office workers, certainly possible for some].
Silicon Valley's permanent, festering housing crisis, now spilling to San Francisco, is pretty much the culprit for the unliveability and unbikeability problem. How could it not be.
[1] https://en.wikipedia.org/wiki/Copenhagen [2] https://en.wikipedia.org/wiki/San_Jose,_California