They quite frankly can't technically, only legally - they're selling a 0 margin good, anyone who has it can basically give away infinite copies at zero cost per additional copy. Anyone who wants it for free will have it for free. They need no more than drop a few words into Google or type the name of something into a fully automatic tool like Sonarr.
It's pointless for them to bother trying to stop piracy, especially of analog content using technical means.
"but it's not perfect, someone could just xyz and abc and get around the system."
DRM is not about being perfect against a dedicated pirate. Just like locks on doors, it's about putting up a few barriers that serve to keep the vast majority of people honest. No one is under any illusions that DRM will stop movies and games from showing up on torrent trackers.
There's a big different between breaking a door down to bypass a lock and pirating a movie via bittorrent though.
It doesn't "keep honest people honest" when piracy is so damn easy regardless of what they do with DRM. The point of that phrase is to increase the effort and motivation necessary to commit a crime - in this case, DRM doesn't do that. With or without DRM any idiot can download the latest Popcorn Time fork and stream movies with 1 click. DRM doesn't hinder the most casual of pirates at all, it only hinders honest customers.
People are pretty wary of using torrents because they're scared of being sued. What DRM on Netflix prevents is you ripping all of the seasons of your favorite shows, with almost no risk of getting caught, and then cancelling your Netflix subscription/sharing the rips with your friend, who is probably not inclined to use torrent sites.
Most people I know who casually pirate things don't even use torrents, they use streaming websites, file lockers, Kodi plugins, etc. Which offer similarly no risk of getting caught. I was simply using Popcorn Time as the extreme example of the level of ease it can be at.
None of these are exactly out-of-the-way high-effort options. There's no increased effort - you just don't bother trying to do so via Netflix. Any of these can be Googled in a few minutes. DRM does nothing to prevent them.
The legal risk you're talking about is just that though - nothing to do with DRM, everything to do with a legal threat. Note that it's more effective than DRM.
Even those who do go out of their way somewhat to improve the piracy experience don't go that far. I wouldn't compare configuring a typical Usenet+Sonarr+CouchPotato+Plex rig to breaking down a door, and that's pretty much the most advanced sort of setup you can get. It may require slightly specialized knowledge, but it doesn't require specialized intent usually. The intent is still the same as that of the casual pirate, it's just a tradeoff of upfront effort for later ease.
So how do we ensure people keep making quality content and software? Should they give it away for free by default and just count on charity?
Seems to me the only ultimate solution is to have some kind of guaranteed basic income, at least for all people that aren't involved in the creation of tangible goods (that can't be copied at zero cost).
How should content creators protect against people who access their content without buying it?