People used to be more mechanically inclined than they are now, rebuilding their own car engines, doing valve jobs, etc. It could still be done. You don’t jump on a dual with no prior experience – you work your way up.
Duals were part of karting almost from the beginning.
Class A - Stock
Class B Stock, Limited, B Open -
Class C Open - Duals
Most drivers today don’t have the “hardware” to run these karts…or the tuning skills. Perhaps too much soy in our diets.
I think people are still mechanically inclined, but we’ve moved into an era of permission-seeking. It’s a strange phenomenon, but I think it’s more a case of people not knowing they can do something themselves and often seeking permission to do the most basic of tasks. This is partly a cultural consequence of the expansion of team-based culture at the track.
But if people saw more of it, I think we’d see more people doing things themselves.
This is why courage matters and should be taught / passed on generationally. 
Oh that looks controversial right there ha… Twin KA (or VLR) would be great.
Down under in Nz and Oz they have some crazy stuff on pavement and dirt. I’ll see if I can find some videos. One had a shifter engine on one side and a direct drive 100cc on the other.
It depends. Since the beginning of the karting scene in my country all drivers were in a team(or a personal mechanic). It was only in the 90s when the national economy started to get better that privateers appeared. Ironically enough more teams appeared after Rotax entered.
Nowadays there are only three privateers in my club, though there are more in another club, but they always bring an employee or guard to help them.
The thing is local teams always try to teach the driver to attend themselves little by little like changing tyres, air pressure to aligning their kart. Obviously it doesn’t matter if the driver isn’t willing to learn, but at least there’s room for change.
Regarding to engines, the only privateer who repaired their engines is totally retired. So things beyond basic maintenance is dead 
