The answer to the question in the quote is: "It's not until someone wins a lawsuit."
The federal government recognizes, and will protect through legal enforcement, an exclusive right of the intellectual property holder to control its distribution.
Copyright infringement only occurs when a court rules that it has because that is the only mechanism through which intellectual property holders can claim a legal right. It is not a "natural right".
Streaming from a "piracy" site is effectively legal for the viewer because they are not infringing on any distribution or resell rights (but the hoster is). If Netflix is mistakenly giving access to all seasons of a show when it only paid for the latest one, how could anyone call the unknowing viewer who is watching Season 1 a pirate?
"Abandonware" pushes this idea even further: as long as there is no reasonable expectation of a successful infringement case being brought against anyone then distribution is also without consequence. Perhaps there is a statue of limitations that might definitive codify this or a "defend or lose it" stipulation as exists with trademarks.