Bar ends & skinny bars are good for racing, but no good for a typical ride which would involve more gnarly terrain & jumps/drops, so cart wheels would not be better for most people, as most people don't race
Most people? I doubt it - I'd have thought the majority of mountain bikes are sold via supermarkets and Halfords to people who use them for riding around the park and commuting, both of which are ideal for 29ers.

