What profit? Netflix offers rentals only, and no sales. And Netflix DRM doesn't prevent any piracy since users who want to illegally retain the copy can do it either way. So what is the reason for them using it? They can simply use sales and have the same profit.
Engaging in proliferating an unethical practice under pretense that "they have no choice" is a very questionable thing. Netflix had a choice, but they chose to do this.
They could exist trying to concentrate on DRM-free distribution. Others managed that: https://www.headweb.com/en/
Of course it wouldn't have the same scale. But we aren't talking about scale - you mentioned existence as if selling something DRM-free is not possible or not sustainable.
But the right owners also license same movies for sale via other channels, and they (I presume) agree to lower price for Neflix because it's only rentals.
Physical media is a very different market with different mechanisms. In the digital space there are no major offerings with selling files with video so far (besides small local examples like Headweb), so there is no segmenting like mentioned above.
