I ride a SWB bike with under-seat steering. The bar-end shifters are a natural contact point if you lean it against a wall, or it falls on the ground.
I've found that the 9-speed Dura-Ace shifters are effectively a disposable item. What seems to happen, if you don't completely destroy them by sliding along the tarmac, is the ring with the indexing detents weakens and cracks when the lever is subjected to horizontal force (hence the non-indexed front shifter seems to be more durable). When it splits, the indexing on half the cassette goes to pot, but friction mode still works. Eventually it disintegrates further and the shifter loses friction, so you have to hold it in place until you get home.
I'm currently running a pair of Microshift bar-ends, to see if they last any longer. So far so good (they work just as well as the Shimano, but lack a switchable friction mode), but the bike has only had one gentle fall on grass (by a newbie rider) in that time. I've been especially careful about contact points when stowing the bike on trains since I worked out that was what was damaging them.
Obviously a trike or velomobile wouldn't have most of these problems. Barakta's ICE trike has one of my orphaned shifters fitted with an extended handle, and that continues to be fine. The drop-barred DF tourer crowd don't seem to think they're particularly unreliable, either.