If anyone is interested in the actual reasons people give, you’re mostly out of luck because there is precious little research, neither of the major parties seem to care about this demographic, and neither do pollsters for the most part. Here’re the results of some research following the 2020 presidential (based on a fairly small sample).
Spoiler: It’s not because they don’t have time.
I made a meme claiming democrats call anyone who says they don’t vote a russian conspiracist, you gave a bunch of (likely incorrect, based on the real data) guesses about why people might not vote.