This. DRM is a courtesy lock on a bathroom door. It makes ripping content enough of a hassle that only people who are willing to put some effort in will bother, and those people are going to find a way around it no matter what. It doesn't have to be unbreakable to have some value to the content owner.
If we accept that enabling DRM on some of their content has some value to Netflix, which it obviously does, and we accept that it doesn't impose unacceptable user experience tradeoffs, which it obviously doesn't, then it is rational for them to enable it on all of their content.
There is probably a hypothetical cost/benefit break-even point where it actually degrades the user experience a little and thus is only acceptable in cases where it is absolutely needed, but it seems unlikely this is significant enough to even be quantifiable.
If we accept that enabling DRM on some of their content has some value to Netflix, which it obviously does, and we accept that it doesn't impose unacceptable user experience tradeoffs, which it obviously doesn't, then it is rational for them to enable it on all of their content.
There is probably a hypothetical cost/benefit break-even point where it actually degrades the user experience a little and thus is only acceptable in cases where it is absolutely needed, but it seems unlikely this is significant enough to even be quantifiable.