I for one have never bumped a bar end with my knees, and thats on bikes with both high and low bars. I have also never shifted gears leaning a bike on something with bar ends. And thats out of about six bikes that have them. I run old suntour friction bar ends on all my bikes that don't have friction downtube(or indexed virtualy permanently set to friction)or friction thumb shifters.

One advantage of bar ends, and I don't think that anyone touched on this, is that most new barends can be set to friction mode. A roadbike generaly goes to a home at night, so when the derailers need to be adjusted its no big deal, either you do it yourself, or take it to a shop.
On a tour, if a cable gets stretched, a derailer bumped out of adjustment, or a part wears so that the indexing is not perfect, then its really nice to be able to go to friction where you can trim the chain so it does not rub or grind on the front derailer, or chatter on the rear cluster. Then, when you have made the miles that you planned for the day without having to stop and screw with adjustments, you can work on it at leasure, or wait till you find a shop.

The only bikes I run indexed on are my mountain bikes, and that because like many have said, its nice to be able to shift fast at a moments notice when needed.
But on a tour, usualy I don't need to do that. In fact, I am usualy in one gear for long periods of time. That would be the granny gear...