Your view seems to be that because you rate it, then so must I. But why would that be so?
I think word has summed it up, really. We all look for different things for our children, so it's not at all surprising that we make different choices. (Those of us who are fortunate enough to be in a position to make choices, that is - I realise that many have no choice.)
I am quite familiar with what goes on in the so-called "top" private schools, and I have many friends who attended such schools. Some are choosing to educate their DCs in this way. Personally, I have not found anything in these schools that I value that I am unable to obtain in the state sector or through extra-curricular activities/family life etc. Parents like happy and word clearly place a different value on some of these things. I don't think any of us are right or wrong.
Ultimately, I think it boils down to values and confidence - what each parent considers to be important for a "good education", the degree of confidence that parents have in their own ability to provide an excellent education in line with those values, and the degree of confidence that they have in their children's ability to flourish and succeed wherever they are.
Obviously, those who have chosen to pay for private schooling believe that it has a value, otherwise they wouldn't spend so much money on it. Meanwhile, those of us who could comfortably afford to pay school fees but choose to use the state system instead feel that there is no real benefit in going private. Ultimately, I guess it will depend on the individual child and the specific range of schools available to you.