I have 30 gears on my road bike, I use all of them (including occaisionally the extreme angle ones) with no "favourite" gears. I shift through the range a lot to keep things moving with an optimal balance of effort speed, I like to enjoy my ride. sometimes I do shift both front and back at about the same time to get just the right gear. Gears ranges may have overlap but that doesnt mean waste! it means that within the overlap range you have even more slight variation, I dont think theres many setups where the gear inches are identical between any two combinations!
Due to alignment problems my knees do hurt when trying to push to big a gear up a hill, I like my triple. I probably wouldnt complain about losing some overlap but I like a low bottom a high top and plenty of steps between!
I live in a very hilly area, with lots of gradient changes I like to make full use of my gears. Sure at one time I used to use a single speed bmx locally when I was a kid (in fact my first bike was fixed and single speed - I hated it) but then I also got off and pushed on some hills back then, and can go far faster and further now... Gears are good - if you have a use for them. If I lived somewhere flatter with occaisional hills Id love a lower maintenenace single speed. Far less hassle Im sure.