I don't really agree. Through tickets are available in 99% of cases for those passengers wanting to be able to check their bags through and retain protection in the event of delays. I would anticipate that the number of journeys where a through ticket/interlining is not available are relatively few.

I do understand that people argue that they have busy lives and itineraries subject to change: well changeable tickets are available for such circumstances.

What doesn't really work is for people to expect to gain from the savings that exist on many separate tickets whilst retaining the benefits of buying one.