In my case from last year, I booked a trip that included Jetconnect flights between Australia and NZ. According to BA, they did not have e-ticketing agreements with Jetconnect so the only option was a paper ticket. I must say I was quite surprised by this and so where most people I encountered on my trip, starting with the lady at the ticketing counter at ARN who gave me a long speech about how paper tickets were no longer used and then turned all red when her system spit my tickets out...