Serious Noob Question: What is so good about Criterion DVDs/BluRays?

Hi,

So as you can see I'm new here. The Criterion Collection only recently came to my attention when I started browsing r/dvdcollection. I hadn't really heard of these Criterion DVDs and BluRays before, but everyone seems to love them and say they are the best. What is so good about them, and what justifies their prices which are generally higher than normal DVDs/Blus? Is it the picture quality? Is it because they do new restorations of old films? Is it the special features? Is it because it is the only way to obtain copies of obscure films that are otherwise out of print? Is it because they are guaranteed to be quality/artistic/important? Is it a combination of all those things?

Sorry if these are dumb questions. I just want to know why I should want to buy Criterions.

Also I have noticed Hulu has over 900 films from the Criterion Collection on Streaming. What is the advantage of owning them on Blu Ray over just streaming them there?

Thank you and I hope you don't hate me for being ignorant.