Even the name of the degree, masters, implies that this is for mastering that subject. I personally take that as a hint that (in general) you should already be intimately acquainted to it before mastering it.

Those years for the bachelor don't just prove you learned some random subjects. They also show that you deliver - you have a topic, you study it, you pass the exam.

The reason you say "I don't need that" is because you have to pay a crapload of money for those 3 years with a dubious ROI. It's a credential racket because they charge you through your nose. And it's cheaper now because online is cheaper. But it's unrealistic to assume you get the same quality for less money, it would sink their normal masters business right? Lots of things are debatable here especially if you dig into the exceptions but generally it might be the difference between takeout/fast food and a good restaurant.

When I see people skipping some degrees and going for the online ones they have to show some damn good practical achievements to convince me that was time worth saving.

I'm pretty sure most of you would refuse to go to a doctor who studied online. Cyber-security can easily turn out to be life or death.