I guess it's what you're into that matters. I am a foodie, and my girlfriend is a foodie, so a vacation is largely about what great food we get to eat. So for us, taking a couple hours to relax with a great meal is really important. As such, ADRs are critical! It would be amazing if we could just decide, "hey, let's go to California Grill tonight!" but unfortunately that's not possible. So we decide where we want to eat, and work our plans accordingly.
I'll mention one anecdote from our trip last year. While waiting for Le Cellier, we saw multiple groups try to walk up and be turned away. One family got angry at their son (who was maybe 9 or 10), because they felt that his desire to ride whatever ride ultimately delayed them kept them from a table (in actuality, it was the Friday after Thanksgiving and that restaurant was completely booked). They said all sorts of really nasty things to him, telling him that it was his fault that they couldn't eat there. In that case, it was them projecting off of a huge mistake that they made in not making reservations.
Unfortunately given the popularity of many of the Disney restaurants, you have to decide what you're going to feel like doing 6 months in advance. Last year (my first in 12 years and my girlfriend's first in 15) there were times when we didn't feel like cutting short what we were doing to make it to dinner, but there were also meals that we are really glad we scheduled in regardless of how it affected our schedule. It's a best guess, really, and once you make your choice, you live with it! By and large we were more glad to have reservations than annoyed at having to run off to them.
So again, I see your point, but it's a matter of personal preference about what a vacation at Disney is all about. If I had to eat nasty counter service food all week, I'd be a cranky boy. But others might not, and that's cool!