Your argument seems to be: "Don't make waves. Don't do anything out of the ordinary."
To many people, having Linux installed on a computer is something that people have no legitimate reason for.
No innovation or individuality. Everyone has to be exactly the same.
Also, your line of reasoning goes against presumption of innocence. The suspect doesn't have to explain why he has that much storage. The police/prosecutor have to explain what criminal acts he's doing with that storage.
An example:
Raw captures (e.g., digitized home movies) can take up a lot of space, even if they're losslessly-compressed with a codec like Huffyuv or Lagarith.
I have five raw captures of the same 2-hour VHS movie sitting on my HDD, as I plan to average them to reduce the appearance of artifacts due to tracking differences. Each capture is losslessly-compressed with Huffyuv and approximately __50GB__.
That's ~250GB right there.