For the same reason "finders keepers" isn't codified law. By that logic, nobody is allowed to controls the means by which their software is run. You don't get to decide if people have to pay you, or if people have to have your permission first, or if they're allowed to (legally) copy it, etc.
AFAIK, many jurisdictions have rules clarifying that any incidental copies, like installing it, or copying it to RAM, or to the various CPU and SSD caches, are necesssary for the operation of the software, and are therefore not counted as breaches of copyright.
If this was not so, copyright holders could sue all the router and switch operators in the world for copying pirated works by merely having the network packets temporarily in their packet buffers.
Yeah, I don't know the law about incidental copies and RAM and stuff. But I think we shouldn't lump that with using a dedicated piece of hardware, because I think there is a difference between the two. Whether that difference is relevant in the law, I'm not sure.
Wouldn't router and switch operators be considered distributors rather than publishers?
>Prior to the Internet, case law was clear that a liability line was drawn between publishers of content and distributors of content; a publisher would be expected to have awareness of material it was publishing and thus should be held liable for any illegal content it published, while a distributor would likely not be aware and thus would be immune.