What is really the purpose of streaming??

In my system, into my DAC, streaming sounds better than CDs ripped to flac on my hard drive.

And for $20/month, I can play about 90% of the albums that have ever been recorded.

In case the internet breaks, I still have all my ripped CDs.  But as long as those tubes are flowing, I'll take a stream, please.

Its mostly about easy access to music.  It can also be about top notch sound but does not have to be.  Same true about records, CDs, whatever.

CD or streaming can both be top notch if done well/right.  Same true with vinyl.    

It is probably easier these days for most people to have a chance at getting top notch sound at an affordable price using streaming.    Also streaming offers many user experience focused features that many will find beneficial in addition to the sound quality.   Of course some will not...

So combine cost, good sound quality and a myriad of value added features available and its easy to see why this is where things are and will continue to go.

I think it is mostly about convenience, but if you use Roon with Tidal it can show you music that you can discover, like, and possibly would have never thought to hear.

There are no sonic differences between cd's and red book 16/44 streams as from Tidal or Qobuz (provided the same DAC is used, of course). The difference is the convenience and the access. The latter in particular is something I value greatly. Suddenly you have access to a very large proportion of all music ever recorded.

Streaming allows you to access more music than you could ever possibly own.  If set up properly, sound quality is not an issue.  There are issues regarding how people can sort through and digest extremely large collections.  Most algorithms are based on "if someone listened to X artist, what else did they listen to".  Most people find that very helpful, but some don't.