Be honest....... how many of you know the major and minor scales in every key and how important do you think this is?
well its not too hard because you only have to really know 4 different patterns ; The major scale starting on string 6, the minor scale starting on string 6, the major scale starting on string 5 and the minor scale starting on string 5. After that you can just move it up and down the fretboard depending on which key you want to play in.

Not too much to learn really but it is useful to know all those 4 patterns
I know prety much all of them and I think it's only important if you're writing your own stuff, and you want to be creative. If you don't really play much and just learn other peoples songs then it's not so important but it's good to know them.
Well if you actually want to play guitar and not just try to learn songs then you absolutely have to know all the diatonic modes IMO. Once you understand how all the modes work and fit together then it's actually pretty easy.
Putting them in every key is pretty easy also. Just move where want the root note to be anywhere on the neck.
If you want to solo or write a song that isn't in those pentatonic boxes then you definitely need to know them.
I know them in every key and I think that it is very important - especially if you plan on playing with others. As for being able to play them on command in every key, I'm working on that